Merge branch 'develop' into coverity_scan

.github/CONTRIBUTING.md

@@ -6,6 +6,10 @@ This project started as a little excuse to exercise some of the cool new C++11 f
 
 To make it as easy as possible for you to contribute and for me to keep an overview, here are a few guidelines which should help us avoid all kinds of unnecessary work or disappointment. And of course, this document is subject to discussion, so please [create an issue](https://github.com/nlohmann/json/issues/new) or a pull request if you find a way to improve it!
 
+## Private reports
+
+Usually, all issues are tracked publicly on [Github](https://github.com/nlohmann/json/issues). If you want to make a private report (e.g., for a vulnerability or to attach an example that is not meant to be publisheed), please send an email to <mail@nlohmann.me>.
+
 ## Prerequisites
 
 Please [create an issue](https://github.com/nlohmann/json/issues/new), assuming one does not already exist, and describe your concern. Note you need a [GitHub account](https://github.com/signup/free) for this.
@@ -57,6 +61,7 @@ Please understand that I cannot accept pull requests changing only file `src/jso
 ## Note
 
 - If you open a pull request, the code will be automatically tested with [Valgrind](http://valgrind.org)'s Memcheck tool to detect memory leaks. Please be aware that the execution with Valgrind _may_ in rare cases yield different behavior than running the code directly. This can result in failing unit tests which run successfully without Valgrind.
+- There is a Makefile target `make pretty` which runs [Artistic Style](http://astyle.sourceforge.net) to fix indentation. If possible, run it before opening the pull request. Otherwise, we shall run it afterward.
 
 ## Please don't
 

.gitignore

@@ -1,16 +1,16 @@
 json_unit
 json_benchmarks
-
 fuzz-testing
 
 *.dSYM
+*.o
+*.gcno
+*.gcda
 
 working
 
-html
+doc/xml
+doc/html
 me.nlohmann.json.docset
 
-android
-doc/xml
-
 benchmarks/files/numbers/*.json

.travis.yml

@@ -1,33 +1,87 @@
+#########################
+# project configuration #
+#########################
+
+# C++ project
 language: cpp
 
 dist: trusty
 sudo: required
 
+
+###################
+# global settings #
+###################
+
 env:
   global:
    # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
    #   via the "travis encrypt" command using the project repo's public key
    - secure: "m89SSgE+ASLO38rSKx7MTXK3n5NkP9bIx95jwY71YEiuFzib30PDJ/DifKnXxBjvy/AkCGztErQRk/8ZCvq+4HXozU2knEGnL/RUitvlwbhzfh2D4lmS3BvWBGS3N3NewoPBrRmdcvnT0xjOGXxtZaJ3P74TkB9GBnlz/HmKORA="
 
-# from http://stackoverflow.com/a/32127147/266378
+
+################
+# build matrix #
+################
+
 matrix:
   include:
+
+  # Valgrind
+
+  - os: linux
+    compiler: gcc
+    env:
+      - COMPILER=g++-4.9
+      - SPECIAL=valgrind
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: [g++-4.9, valgrind]
+    after_success:
+      - valgrind --error-exitcode=1 --leak-check=full test/json_unit
+
+  # cppcheck
+
+  - os: linux
+    compiler: gcc
+    env:
+      - COMPILER=g++-4.9
+      - SPECIAL=cppcheck
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: [g++-4.9, cppcheck]
+    after_success:
+      - make cppcheck
+
+  # Coveralls (http://gronlier.fr/blog/2015/01/adding-code-coverage-to-your-c-project/)
+
   - os: linux
     compiler: gcc
     addons:
       apt:
         sources: ['ubuntu-toolchain-r-test']
-          packages: ['g++-4.9', 'valgrind', 'python-pip', 'python-yaml']
+        packages: ['g++-4.9', 'ruby']
     before_script:
-        - pip install --user git+git://github.com/eddyxu/cpp-coveralls.git
+      - wget http://ftp.de.debian.org/debian/pool/main/l/lcov/lcov_1.11.orig.tar.gz
+      - tar xf lcov_1.11.orig.tar.gz
+      - sudo make -C lcov-1.11/ install
+      - gem install coveralls-lcov
     after_success:
       - make clean
-        - touch src/json.hpp
+      - CXXFLAGS="--coverage -g -O0" CPPFLAGS="-DNDEBUG" make
-        - make json_unit CXXFLAGS="-fprofile-arcs -ftest-coverage -std=c++11 -lstdc++" CXX=$COMPILER
+      - test/json_unit "*"
-        - ./json_unit "*"
+      - coveralls --build-root test --exclude src/catch.hpp --exclude src/unit-algorithms.cpp --exclude src/unit-allocator.cpp --exclude src/unit-capacity.cpp --exclude src/unit-class_const_iterator.cpp --exclude src/unit-class_iterator.cpp --exclude src/unit-class_lexer.cpp --exclude src/unit-class_parser.cpp --exclude src/unit-comparison.cpp --exclude src/unit-concepts.cpp --exclude src/unit-constructor1.cpp --exclude src/unit-constructor2.cpp --exclude src/unit-convenience.cpp --exclude src/unit-conversions.cpp --exclude src/unit-deserialization.cpp --exclude src/unit-element_access1.cpp --exclude src/unit-element_access2.cpp --exclude src/unit-inspection.cpp --exclude src/unit-iterator_wrapper.cpp --exclude src/unit-iterators1.cpp --exclude src/unit-iterators2.cpp --exclude src/unit-json_patch.cpp --exclude src/unit-json_pointer.cpp --exclude src/unit-modifiers.cpp --exclude src/unit-pointer_access.cpp --exclude src/unit-readme.cpp --exclude src/unit-reference_access.cpp --exclude src/unit-regression.cpp --exclude src/unit-serialization.cpp --exclude src/unit-testsuites.cpp --exclude src/unit-unicode.cpp --include ../src/json.hpp --gcov-options '\-lp' --gcov 'gcov-4.9'
-        - coveralls --exclude test/src/catch.hpp --exclude test/src/unit.cpp --include src/json.hpp --gcov-options '\-lp' --gcov 'gcov-4.9'
+      - lcov --directory src --directory test/src --capture --output-file coverage.info --rc lcov_branch_coverage=1 --no-external
-        - bash <(curl -s https://codecov.io/bash)
+      - lcov --remove coverage.info 'test/src/*' --output-file coverage.info --rc lcov_branch_coverage=1
-      env: COMPILER=g++-4.9
+      - lcov --list coverage.info --rc lcov_branch_coverage=1
+      - coveralls-lcov --repo-token F9bs4Nop10JRgqPQXRcifyQKYhb3FczkS coverage.info
+    env:
+      - COMPILER=g++-4.9
+      - SPECIAL=coveralls
+
+  # Coverity (only for branch coverity_scan)
 
   - os: linux
     compiler: gcc
@@ -44,133 +98,207 @@ matrix:
         build_command_prepend: "make clean ; sudo cp $(which g++-5) $(which g++)"
         build_command: "make"
         branch_pattern: coverity_scan
-      env: COMPILER=g++-5
-
-    - os: linux
-      compiler: gcc
-      addons:
-        apt:
-          sources: ['ubuntu-toolchain-r-test']
-          packages: ['g++-6', 'valgrind']
-      env: COMPILER=g++-6
-
-    # from https://github.com/travis-ci/travis-ci/issues/6120
-    - os: linux
     env:
-        - LLVM_VERSION=3.8.0
+      - COMPILER=g++-5
-        - LLVM_ARCHIVE_PATH=$HOME/clang+llvm.tar.xz
+      - SPECIAL=coverity
-        - COMPILER=clang++
-        - CPPFLAGS="-I $HOME/clang-$LLVM_VERSION/include/c++/v1"
-        - CXXFLAGS=-lc++
-        - PATH=$HOME/clang-$LLVM_VERSION/bin:$PATH
-        - LD_LIBRARY_PATH=$HOME/clang-$LLVM_VERSION/lib:$LD_LIBRARY_PATH
-      before_install:
-       - wget http://llvm.org/releases/$LLVM_VERSION/clang+llvm-$LLVM_VERSION-x86_64-linux-gnu-ubuntu-14.04.tar.xz -O $LLVM_ARCHIVE_PATH
-       - mkdir $HOME/clang-$LLVM_VERSION
-       - tar xf $LLVM_ARCHIVE_PATH -C $HOME/clang-$LLVM_VERSION --strip-components 1
 
-    # Clang 3.5 is not able to compile the code,
+  # OSX / Clang
-    # see https://travis-ci.org/nlohmann/json/jobs/126720186
-
-#    - os: linux
-#      compiler: clang
-#      addons:
-#        apt:
-#          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.6']
-#          packages: ['clang-3.6', 'valgrind']
-#      env: COMPILER=clang++-3.6
-#
-#    - os: linux
-#      compiler: clang
-#      addons:
-#        apt:
-#          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
-#          packages: ['clang-3.7', 'valgrind']
-#      env: COMPILER=clang++-3.7
-#
-#    - os: linux
-#      compiler: clang
-#      addons:
-#        apt:
-#          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.8']
-#          packages: ['clang-3.8', 'valgrind']
-#      env: COMPILER=clang++-3.8
-
-  #  - os: linux
-  #    compiler: clang
-  #    addons:
-  #      apt:
-  #        sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise']
-  #        packages: ['clang-3.9', 'valgrind']
-  #    env: COMPILER=clang++-3.9
 
   - os: osx
     osx_image: beta-xcode6.1
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: beta-xcode6.2
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: beta-xcode6.3
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: xcode6.4
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: xcode7.1
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: xcode7.2
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: xcode7.3
-      compiler: clang
-      env:
-       - COMPILER=clang
-       - CXXFLAGS=-lstdc++
 
   - os: osx
     osx_image: xcode8
+
+  # Linux / GCC
+
+  - os: linux
+    compiler: gcc
+    env: COMPILER=g++-4.9
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: g++-4.9
+
+  - os: linux
+    compiler: gcc
+    env: COMPILER=g++-5
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: g++-5
+
+  - os: linux
+    compiler: gcc
+    env: COMPILER=g++-6
+    addons:
+      apt:
+        sources: ['ubuntu-toolchain-r-test']
+        packages: g++-6
+
+  # Linux / Clang
+
+  - os: linux
+    env: LLVM_VERSION=3.6.0
     compiler: clang
-      env:
+
-       - COMPILER=clang
+  - os: linux
-       - CXXFLAGS=-lstdc++
+    env: LLVM_VERSION=3.6.1
+    compiler: clang
+
+  - os: linux
+    env: LLVM_VERSION=3.6.2
+    compiler: clang
+
+  - os: linux
+    env: LLVM_VERSION=3.7.0
+    compiler: clang
+
+  - os: linux
+    env: LLVM_VERSION=3.7.1
+    compiler: clang
+
+  - os: linux
+    env: LLVM_VERSION=3.8.0
+    compiler: clang
+
+  - os: linux
+    env: LLVM_VERSION=3.8.1
+    compiler: clang
+
+#####################
+# installation step #
+#####################
+
+# set directories to cache
+cache:
+  directories:
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.6.2
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.6.1
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.6.0
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.7.0
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.7.1
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.8.0
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.8.1
+
+
+install:
+  # create deps dir if not existing
+  - DEPS_DIR="${TRAVIS_BUILD_DIR}/deps"
+  - mkdir -p ${DEPS_DIR}
+
+  # make sure CXX is correctly set
+  - if [[ "${COMPILER}" != "" ]]; then export CXX=${COMPILER}; fi
+
+  # install LLVM/clang when LLVM_VERSION is set
+  - |
+     if [[ "${LLVM_VERSION}" != "" ]]; then
+       LLVM_DIR=${DEPS_DIR}/llvm-${LLVM_VERSION}
+       if [[ -z "$(ls -A ${LLVM_DIR})" ]]; then
+         LLVM_URL="http://llvm.org/releases/${LLVM_VERSION}/llvm-${LLVM_VERSION}.src.tar.xz"
+         LIBCXX_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxx-${LLVM_VERSION}.src.tar.xz"
+         LIBCXXABI_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxxabi-${LLVM_VERSION}.src.tar.xz"
+         CLANG_URL="http://llvm.org/releases/${LLVM_VERSION}/clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-14.04.tar.xz"
+         mkdir -p ${LLVM_DIR} ${LLVM_DIR}/build ${LLVM_DIR}/projects/libcxx ${LLVM_DIR}/projects/libcxxabi ${LLVM_DIR}/clang
+         travis_retry wget --quiet -O - ${LLVM_URL}      | tar --strip-components=1 -xJ -C ${LLVM_DIR}
+         travis_retry wget --quiet -O - ${LIBCXX_URL}    | tar --strip-components=1 -xJ -C ${LLVM_DIR}/projects/libcxx
+         travis_retry wget --quiet -O - ${LIBCXXABI_URL} | tar --strip-components=1 -xJ -C ${LLVM_DIR}/projects/libcxxabi
+         travis_retry wget --quiet -O - ${CLANG_URL}     | tar --strip-components=1 -xJ -C ${LLVM_DIR}/clang
+         (cd ${LLVM_DIR}/build && cmake .. -DCMAKE_INSTALL_PREFIX=${LLVM_DIR}/install -DCMAKE_CXX_COMPILER=clang++)
+         (cd ${LLVM_DIR}/build/projects/libcxx && make install -j2)
+         (cd ${LLVM_DIR}/build/projects/libcxxabi && make install -j2)
+       fi
+       export CXXFLAGS="-nostdinc++ -isystem ${LLVM_DIR}/install/include/c++/v1"
+       export LDFLAGS="-L ${LLVM_DIR}/install/lib -l c++ -l c++abi"
+       export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${LLVM_DIR}/install/lib"
+       export PATH="${LLVM_DIR}/clang/bin:${PATH}"
+     fi
+
+################
+# build script #
+################
 
 script:
+  # show OS/compiler version
   - uname -a
-  - $COMPILER --version
+  - $CXX --version
-  - make CXX=$COMPILER
+
-  - ./json_unit "*"
+  # compile
-  - if [ `which valgrind` ]; then
+  - make
-    valgrind --error-exitcode=1 --leak-check=full ./json_unit ;
+
-    fi
+  # execute unit tests
+  - test/json_unit "*"
+
+  # check if homebrew works (only checks develop branch)
   - if [ `which brew` ]; then
     brew update ;
     brew tap nlohmann/json ;
     brew install nlohmann_json --HEAD ;
     brew test nlohmann_json ;
     fi
+
+#language: cpp
+#
+#dist: trusty
+#sudo: required
+#
+#env:
+#  global:
+#   # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
+#   #   via the "travis encrypt" command using the project repo's public key
+#   - secure: "m89SSgE+ASLO38rSKx7MTXK3n5NkP9bIx95jwY71YEiuFzib30PDJ/DifKnXxBjvy/AkCGztErQRk/8ZCvq+4HXozU2knEGnL/RUitvlwbhzfh2D4lmS3BvWBGS3N3NewoPBrRmdcvnT0xjOGXxtZaJ3P74TkB9GBnlz/HmKORA="
+#
+## from http://stackoverflow.com/a/32127147/266378
+#matrix:
+#  include:
+#    - os: linux
+#      compiler: gcc
+#      addons:
+#        apt:
+#          sources: ['ubuntu-toolchain-r-test']
+#          packages: ['g++-4.9', 'valgrind', 'python-pip', 'python-yaml']
+#      before_script:
+#        - pip install --user git+git://github.com/eddyxu/cpp-coveralls.git
+#      after_success:
+#        - make clean
+#        - touch src/json.hpp
+#        - make json_unit CXXFLAGS="-fprofile-arcs -ftest-coverage -std=c++11 -lstdc++" CXX=$COMPILER
+#        - test/json_unit "*"
+#        - coveralls --build-root test --exclude src/catch.hpp --exclude src/unit-algorithms.cpp --exclude src/unit-allocator.cpp --exclude src/unit-capacity.cpp --exclude src/unit-class_const_iterator.cpp --exclude src/unit-class_iterator.cpp --exclude src/unit-class_lexer.cpp --exclude src/unit-class_parser.cpp --exclude src/unit-comparison.cpp --exclude src/unit-concepts.cpp --exclude src/unit-constructor1.cpp --exclude src/unit-constructor2.cpp --exclude src/unit-convenience.cpp --exclude src/unit-conversions.cpp --exclude src/unit-deserialization.cpp --exclude src/unit-element_access1.cpp --exclude src/unit-element_access2.cpp --exclude src/unit-inspection.cpp --exclude src/unit-iterator_wrapper.cpp --exclude src/unit-iterators1.cpp --exclude src/unit-iterators2.cpp --exclude src/unit-json_patch.cpp --exclude src/unit-json_pointer.cpp --exclude src/unit-modifiers.cpp --exclude src/unit-pointer_access.cpp --exclude src/unit-readme.cpp --exclude src/unit-reference_access.cpp --exclude src/unit-regression.cpp --exclude src/unit-serialization.cpp --exclude src/unit-testsuites.cpp --exclude src/unit-unicode.cpp --include ../src/json.hpp --gcov-options '\-lp' --gcov 'gcov-4.9'
+#      env: COMPILER=g++-4.9  
+#
+#    - os: linux
+#      compiler: gcc
+#      before_install: echo -n | openssl s_client -connect scan.coverity.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sudo tee -a /etc/ssl/certs/ca-certificates.crt
+#      addons:
+#        apt:
+#          sources: ['ubuntu-toolchain-r-test']
+#          packages: ['g++-5', 'valgrind']
+#        coverity_scan:
+#          project:
+#            name: "nlohmann/json"
+#            description: "Build submitted via Travis CI"
+#          notification_email: niels.lohmann@gmail.com
+#          build_command_prepend: "make clean ; sudo cp $(which g++-5) $(which g++)"
+#          build_command: "make"
+#          branch_pattern: coverity_scan
+#      env: COMPILER=g++-5
+#

Makefile

@@ -12,18 +12,23 @@ clean:
 	rm -fr json_unit json_benchmarks fuzz fuzz-testing *.dSYM
 	rm -fr benchmarks/files/numbers/*.json
 	$(MAKE) clean -Cdoc
+	$(MAKE) clean -Ctest
 
 
 ##########################################################################
 # unit tests
 ##########################################################################
 
-# additional flags
+# build unit tests
-FLAGS = -Wall -Wextra -pedantic -Weffc++ -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wmissing-declarations -Wmissing-include-dirs -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wsign-conversion -Wsign-promo -Wstrict-overflow=5 -Wswitch -Wundef -Wno-unused -Wnon-virtual-dtor -Wreorder -Wdeprecated -Wfloat-equal
+json_unit:
+	@$(MAKE) -C test
 
-# build unit tests (TODO: Does this want its own makefile?)
+# run unit tests
-json_unit: test/src/unit.cpp src/json.hpp test/src/catch.hpp
+check: json_unit
-	$(CXX) -std=c++11 $(CXXFLAGS) $(FLAGS) $(CPPFLAGS) -I src -I test $< $(LDFLAGS) -o $@
+	test/json_unit "*"
+
+check-fast: json_unit
+	test/json_unit
 
 
 ##########################################################################
@@ -59,8 +64,7 @@ fuzz: test/src/fuzz.cpp src/json.hpp
 
 # call cppcheck on the main header file
 cppcheck:
-	cppcheck --enable=all --inconclusive --std=c++11 src/json.hpp
+	cppcheck --enable=warning --inconclusive --force --std=c++11 src/json.hpp --error-exitcode=1
-
 
 ##########################################################################
 # maintainer targets
@@ -77,7 +81,8 @@ pretty:
 	   --indent-col1-comments --pad-oper --pad-header --align-pointer=type \
 	   --align-reference=type --add-brackets --convert-tabs --close-templates \
 	   --lineend=linux --preserve-date --suffix=none --formatted \
-	   src/json.hpp src/json.hpp.re2c test/src/unit.cpp test/src/fuzz.cpp benchmarks/benchmarks.cpp doc/examples/*.cpp
+	   src/json.hpp src/json.hpp.re2c test/src/*.cpp \
+	   benchmarks/benchmarks.cpp doc/examples/*.cpp
 
 
 ##########################################################################
@@ -87,7 +92,7 @@ pretty:
 # benchmarks
 json_benchmarks: benchmarks/benchmarks.cpp benchmarks/benchpress.hpp benchmarks/cxxopts.hpp src/json.hpp
 	cd benchmarks/files/numbers ; python generate.py
-	$(CXX) -std=c++11 $(CXXFLAGS) -O3 -flto -I src -I benchmarks $< $(LDFLAGS) -o $@
+	$(CXX) -std=c++11 $(CXXFLAGS) -DNDEBUG -O3 -flto -I src -I benchmarks $< $(LDFLAGS) -o $@
 	./json_benchmarks
 
 

README.md

@@ -9,6 +9,7 @@
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/nlohmann/json/master/LICENSE.MIT)
 [![Github Releases](https://img.shields.io/github/release/nlohmann/json.svg)](https://github.com/nlohmann/json/releases)
 [![Github Issues](https://img.shields.io/github/issues/nlohmann/json.svg)](http://github.com/nlohmann/json/issues)
+[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/289/badge)](https://bestpractices.coreinfrastructure.org/projects/289)
 
 ## Design goals
 
@@ -18,7 +19,7 @@ There are myriads of [JSON](http://json.org) libraries out there, and each may e
 
 - **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/src/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.
 
-- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/blob/master/test/src/unit.cpp) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) that there are no memory leaks.
+- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/blob/master/test/src/unit.cpp) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) that there are no memory leaks. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
 
 Other aspects were not so important to us:
 
@@ -416,7 +417,13 @@ The following compilers are currently used in continuous integration at [Travis]
 | GCC 4.9.3       | Ubuntu 14.04.4 LTS           | g++-4.9 (Ubuntu 4.9.3-8ubuntu2~14.04) 4.9.3 |
 | GCC 5.3.0       | Ubuntu 14.04.4 LTS           | g++-5 (Ubuntu 5.3.0-3ubuntu1~14.04) 5.3.0 20151204 |
 | GCC 6.1.1       | Ubuntu 14.04.4 LTS           | g++-6 (Ubuntu 6.1.1-3ubuntu11~14.04.1) 6.1.1 20160511 |
+| Clang 3.6.0     | Ubuntu 14.04.4 LTS           | clang version 3.6.0 (tags/RELEASE_360/final) |
+| Clang 3.6.1     | Ubuntu 14.04.4 LTS           | clang version 3.6.1 (tags/RELEASE_361/final) |
+| Clang 3.6.2     | Ubuntu 14.04.4 LTS           | clang version 3.6.2 (tags/RELEASE_362/final) |
+| Clang 3.7.0     | Ubuntu 14.04.4 LTS           | clang version 3.7.0 (tags/RELEASE_370/final) |
+| Clang 3.7.1     | Ubuntu 14.04.4 LTS           | clang version 3.7.1 (tags/RELEASE_371/final) |
 | Clang 3.8.0     | Ubuntu 14.04.4 LTS           | clang version 3.8.0 (tags/RELEASE_380/final) |
+| Clang 3.8.1     | Ubuntu 14.04.4 LTS           | clang version 3.8.1 (tags/RELEASE_381/final) |
 | Clang Xcode 6.1 | Darwin Kernel Version 13.4.0 (OSX 10.9.5) | Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn) |
 | Clang Xcode 6.2 | Darwin Kernel Version 13.4.0 (OSX 10.9.5) | Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn) |
 | Clang Xcode 6.3 | Darwin Kernel Version 14.3.0 (OSX 10.10.3) | Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn) |
@@ -492,7 +499,7 @@ Thanks a lot for helping out!
 
 ## Notes
 
-- The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](http://en.cppreference.com/w/cpp/error/assert).
+- The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](http://en.cppreference.com/w/cpp/error/assert). In particular, note [`operator[]`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a2e26bd0b0168abb61f67ad5bcd5b9fa1.html#a2e26bd0b0168abb61f67ad5bcd5b9fa1) implements **unchecked access** for const objects: If the given key is not present, the behavior is undefined (think of a dereferenced null pointer) and yields an [assertion failure](https://github.com/nlohmann/json/issues/289) if assertions are switched on. If you are not sure whether an element in an object exists, use checked access with the [`at()` function](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a674de1ee73e6bf4843fc5dc1351fb726.html#a674de1ee73e6bf4843fc5dc1351fb726).
 - As the exact type of a number is not defined in the [JSON specification](http://rfc7159.net/rfc7159), this library tries to choose the best fitting C++ number type automatically. As a result, the type `double` may be used to store numbers which may yield [**floating-point exceptions**](https://github.com/nlohmann/json/issues/181) in certain rare situations if floating-point exceptions have been unmasked in the calling code. These exceptions are not caused by the library and need to be fixed in the calling code, such as by re-masking the exceptions prior to calling library functions.
 
 
@@ -501,11 +508,10 @@ Thanks a lot for helping out!
 To compile and run the tests, you need to execute
 
 ```sh
-$ make
+$ make check
-$ ./json_unit "*"
 
 ===============================================================================
-All tests passed (8905012 assertions in 32 test cases)
+All tests passed (8905099 assertions in 32 test cases)
 ```
 
 For more information, have a look at the file [.travis.yml](https://github.com/nlohmann/json/blob/master/.travis.yml).

src/json.hpp

@@ -1843,7 +1843,8 @@ class basic_json
     @param[in] first begin of the range to copy from (included)
     @param[in] last end of the range to copy from (excluded)
 
-    @pre Iterators @a first and @a last must be initialized.
+    @pre Iterators @a first and @a last must be initialized. **This
+         precondition is enforced with an assertion.**
 
     @throw std::domain_error if iterators are not compatible; that is, do not
     belong to the same JSON value; example: `"iterators are not compatible"`
@@ -3509,6 +3510,9 @@ class basic_json
 
     @return const reference to the element at key @a key
 
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
     @throw std::domain_error if JSON is not an object; example: `"cannot use
     operator[] with null"`
 
@@ -3667,6 +3671,9 @@ class basic_json
 
     @return const reference to the element at key @a key
 
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
     @throw std::domain_error if JSON is not an object; example: `"cannot use
     operator[] with null"`
 
@@ -3867,7 +3874,8 @@ class basic_json
     @complexity Constant.
 
     @pre The JSON value must not be `null` (would throw `std::out_of_range`)
-    or an empty array or object (undefined behavior, guarded by assertions).
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
     @post The JSON value remains unchanged.
 
     @throw std::out_of_range when called on `null` value
@@ -3909,7 +3917,8 @@ class basic_json
     @complexity Constant.
 
     @pre The JSON value must not be `null` (would throw `std::out_of_range`)
-    or an empty array or object (undefined behavior, guarded by assertions).
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
     @post The JSON value remains unchanged.
 
     @throw std::out_of_range when called on `null` value.
@@ -6592,8 +6601,8 @@ class basic_json
     @note An iterator is called *initialized* when a pointer to a JSON value
           has been set (e.g., by a constructor or a copy assignment). If the
           iterator is default-constructed, it is *uninitialized* and most
-          methods are undefined. The library uses assertions to detect calls
+          methods are undefined. **The library uses assertions to detect calls
-          on uninitialized iterators.
+          on uninitialized iterators.**
 
     @requirement The class satisfies the following concept requirements:
     - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
@@ -7725,7 +7734,7 @@ class basic_json
                     };
                     if ((m_limit - m_cursor) < 5)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yybm[0 + yych] & 32)
@@ -7859,7 +7868,7 @@ basic_json_parser_6:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yybm[0 + yych] & 32)
@@ -7929,7 +7938,7 @@ basic_json_parser_15:
                     m_marker = ++m_cursor;
                     if ((m_limit - m_cursor) < 3)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yybm[0 + yych] & 64)
@@ -8022,7 +8031,7 @@ basic_json_parser_31:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
 basic_json_parser_32:
@@ -8059,7 +8068,7 @@ basic_json_parser_36:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= 'e')
@@ -8203,7 +8212,7 @@ basic_json_parser_43:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= '@')
@@ -8239,7 +8248,7 @@ basic_json_parser_44:
                     m_marker = ++m_cursor;
                     if ((m_limit - m_cursor) < 3)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= 'D')
@@ -8280,7 +8289,7 @@ basic_json_parser_47:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= '/')
@@ -8322,7 +8331,7 @@ basic_json_parser_54:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= '@')
@@ -8376,7 +8385,7 @@ basic_json_parser_60:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= '@')
@@ -8417,7 +8426,7 @@ basic_json_parser_63:
                     ++m_cursor;
                     if (m_limit <= m_cursor)
                     {
-                        yyfill();    // LCOV_EXCL_LINE;
+                        yyfill();
                     }
                     yych = *m_cursor;
                     if (yych <= '@')
@@ -8883,7 +8892,8 @@ basic_json_parser_63:
             {
                 case lexer::token_type::begin_object:
                 {
-                    if (keep and (not callback or (keep = callback(depth++, parse_event_t::object_start, result))))
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::object_start, result)) != 0)))
                     {
                         // explicitly set result to object to cope with {}
                         result.m_type = value_t::object;
@@ -8961,7 +8971,8 @@ basic_json_parser_63:
 
                 case lexer::token_type::begin_array:
                 {
-                    if (keep and (not callback or (keep = callback(depth++, parse_event_t::array_start, result))))
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::array_start, result)) != 0)))
                     {
                         // explicitly set result to object to cope with []
                         result.m_type = value_t::array;
@@ -9475,7 +9486,7 @@ basic_json_parser_63:
         }
 
         /// split the string input to reference tokens
-        static std::vector<std::string> split(std::string reference_string)
+        static std::vector<std::string> split(const std::string& reference_string)
         {
             std::vector<std::string> result;
 
@@ -10203,7 +10214,7 @@ basic_json_parser_63:
     */
     static basic_json diff(const basic_json& source,
                            const basic_json& target,
-                           std::string path = "")
+                           const std::string& path = "")
     {
         // the patch
         basic_json result(value_t::array);

src/json.hpp.re2c

@@ -1843,7 +1843,8 @@ class basic_json
     @param[in] first begin of the range to copy from (included)
     @param[in] last end of the range to copy from (excluded)
 
-    @pre Iterators @a first and @a last must be initialized.
+    @pre Iterators @a first and @a last must be initialized. **This
+         precondition is enforced with an assertion.**
 
     @throw std::domain_error if iterators are not compatible; that is, do not
     belong to the same JSON value; example: `"iterators are not compatible"`
@@ -3509,6 +3510,9 @@ class basic_json
 
     @return const reference to the element at key @a key
 
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
     @throw std::domain_error if JSON is not an object; example: `"cannot use
     operator[] with null"`
 
@@ -3667,6 +3671,9 @@ class basic_json
 
     @return const reference to the element at key @a key
 
+    @pre The element with key @a key must exist. **This precondition is
+         enforced with an assertion.**
+
     @throw std::domain_error if JSON is not an object; example: `"cannot use
     operator[] with null"`
 
@@ -3867,7 +3874,8 @@ class basic_json
     @complexity Constant.
 
     @pre The JSON value must not be `null` (would throw `std::out_of_range`)
-    or an empty array or object (undefined behavior, guarded by assertions).
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
     @post The JSON value remains unchanged.
 
     @throw std::out_of_range when called on `null` value
@@ -3909,7 +3917,8 @@ class basic_json
     @complexity Constant.
 
     @pre The JSON value must not be `null` (would throw `std::out_of_range`)
-    or an empty array or object (undefined behavior, guarded by assertions).
+    or an empty array or object (undefined behavior, **guarded by
+    assertions**).
     @post The JSON value remains unchanged.
 
     @throw std::out_of_range when called on `null` value.
@@ -6592,8 +6601,8 @@ class basic_json
     @note An iterator is called *initialized* when a pointer to a JSON value
           has been set (e.g., by a constructor or a copy assignment). If the
           iterator is default-constructed, it is *uninitialized* and most
-          methods are undefined. The library uses assertions to detect calls
+          methods are undefined. **The library uses assertions to detect calls
-          on uninitialized iterators.
+          on uninitialized iterators.**
 
     @requirement The class satisfies the following concept requirements:
     - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
@@ -7689,7 +7698,7 @@ class basic_json
                     re2c:define:YYCURSOR  = m_cursor;
                     re2c:define:YYLIMIT   = m_limit;
                     re2c:define:YYMARKER  = m_marker;
-                    re2c:define:YYFILL    = "yyfill(); // LCOV_EXCL_LINE";
+                    re2c:define:YYFILL    = "yyfill()";
                     re2c:yyfill:parameter = 0;
                     re2c:indent:string    = "    ";
                     re2c:indent:top       = 1;
@@ -8180,7 +8189,8 @@ class basic_json
             {
                 case lexer::token_type::begin_object:
                 {
-                    if (keep and (not callback or (keep = callback(depth++, parse_event_t::object_start, result))))
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::object_start, result)) != 0)))
                     {
                         // explicitly set result to object to cope with {}
                         result.m_type = value_t::object;
@@ -8258,7 +8268,8 @@ class basic_json
 
                 case lexer::token_type::begin_array:
                 {
-                    if (keep and (not callback or (keep = callback(depth++, parse_event_t::array_start, result))))
+                    if (keep and (not callback
+                                  or ((keep = callback(depth++, parse_event_t::array_start, result)) != 0)))
                     {
                         // explicitly set result to object to cope with []
                         result.m_type = value_t::array;
@@ -8772,7 +8783,7 @@ class basic_json
         }
 
         /// split the string input to reference tokens
-        static std::vector<std::string> split(std::string reference_string)
+        static std::vector<std::string> split(const std::string& reference_string)
         {
             std::vector<std::string> result;
 
@@ -9500,7 +9511,7 @@ class basic_json
     */
     static basic_json diff(const basic_json& source,
                            const basic_json& target,
-                           std::string path = "")
+                           const std::string& path = "")
     {
         // the patch
         basic_json result(value_t::array);

test/CMakeLists.txt

@@ -3,6 +3,36 @@ set(JSON_UNITTEST_TARGET_NAME "json_unit")
 add_executable(${JSON_UNITTEST_TARGET_NAME}
     "src/catch.hpp"
     "src/unit.cpp"
+    "src/unit-algorithms.cpp"
+    "src/unit-allocator.cpp"
+    "src/unit-capacity.cpp"
+    "src/unit-class_const_iterator.cpp"
+    "src/unit-class_iterator.cpp"
+    "src/unit-class_lexer.cpp"
+    "src/unit-class_parser.cpp"
+    "src/unit-comparison.cpp"
+    "src/unit-concepts.cpp"
+    "src/unit-constructor1.cpp"
+    "src/unit-constructor2.cpp"
+    "src/unit-convenience.cpp"
+    "src/unit-conversions.cpp"
+    "src/unit-deserialization.cpp"
+    "src/unit-element_access1.cpp"
+    "src/unit-element_access2.cpp"
+    "src/unit-inspection.cpp"
+    "src/unit-iterator_wrapper.cpp"
+    "src/unit-iterators1.cpp"
+    "src/unit-iterators2.cpp"
+    "src/unit-json_patch.cpp"
+    "src/unit-json_pointer.cpp"
+    "src/unit-modifiers.cpp"
+    "src/unit-pointer_access.cpp"
+    "src/unit-readme.cpp"
+    "src/unit-reference_access.cpp"
+    "src/unit-regression.cpp"
+    "src/unit-serialization.cpp"
+    "src/unit-testsuites.cpp"
+    "src/unit-unicode.cpp"
 )
 
 set_target_properties(${JSON_UNITTEST_TARGET_NAME} PROPERTIES

test/Makefile

@@ -0,0 +1,54 @@
+##########################################################################
+# unit tests
+##########################################################################
+
+# additional flags
+CXXFLAGS += -std=c++11 -Wall -Wextra -pedantic -Weffc++ -Wcast-align -Wcast-qual -Wno-ctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wmissing-declarations -Wmissing-include-dirs -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wsign-conversion -Wsign-promo -Wstrict-overflow=5 -Wswitch -Wundef -Wno-unused -Wnon-virtual-dtor -Wreorder -Wdeprecated -Wno-float-equal
+CPPFLAGS += -I ../src -I .
+
+SOURCES = src/unit.cpp \
+          src/unit-algorithms.cpp \
+          src/unit-allocator.cpp \
+          src/unit-capacity.cpp \
+          src/unit-class_const_iterator.cpp \
+          src/unit-class_iterator.cpp \
+          src/unit-class_lexer.cpp \
+          src/unit-class_parser.cpp \
+          src/unit-comparison.cpp \
+          src/unit-concepts.cpp \
+          src/unit-constructor1.cpp \
+          src/unit-constructor2.cpp \
+          src/unit-convenience.cpp \
+          src/unit-conversions.cpp \
+          src/unit-deserialization.cpp \
+          src/unit-element_access1.cpp \
+          src/unit-element_access2.cpp \
+          src/unit-inspection.cpp \
+          src/unit-iterator_wrapper.cpp \
+          src/unit-iterators1.cpp \
+          src/unit-iterators2.cpp \
+          src/unit-json_patch.cpp \
+          src/unit-json_pointer.cpp \
+          src/unit-modifiers.cpp \
+          src/unit-pointer_access.cpp \
+          src/unit-readme.cpp \
+          src/unit-reference_access.cpp \
+          src/unit-regression.cpp \
+          src/unit-serialization.cpp \
+          src/unit-unicode.cpp \
+          src/unit-testsuites.cpp
+
+OBJECTS = $(SOURCES:.cpp=.o)
+
+all: json_unit
+
+json_unit: $(OBJECTS) ../src/json.hpp src/catch.hpp
+	@echo "[CXXLD] $@"
+	@$(CXX) $(CXXFLAGS) $(LDFLAGS) $(OBJECTS) -o $@
+
+%.o: %.cpp ../src/json.hpp src/catch.hpp
+	@echo "[CXX]   $@"
+	@$(CXX) $(CXXFLAGS) $(CPPFLAGS) -c $< -o $@
+
+clean:
+	rm -fr json_unit $(OBJECTS) $(SOURCES:.cpp=.gcno) $(SOURCES:.cpp=.gcda)

test/src/unit-algorithms.cpp

@@ -0,0 +1,318 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("algorithms")
+{
+    json j_array = {13, 29, 3, {{"one", 1}, {"two", 2}}, true, false, {1, 2, 3}, "foo", "baz"};
+    json j_object = {{"one", 1}, {"two", 2}};
+
+    SECTION("non-modifying sequence operations")
+    {
+        SECTION("std::all_of")
+        {
+            CHECK(std::all_of(j_array.begin(), j_array.end(), [](const json & value)
+            {
+                return value.size() > 0;
+            }));
+            CHECK(std::all_of(j_object.begin(), j_object.end(), [](const json & value)
+            {
+                return value.type() == json::value_t::number_integer;
+            }));
+        }
+
+        SECTION("std::any_of")
+        {
+            CHECK(std::any_of(j_array.begin(), j_array.end(), [](const json & value)
+            {
+                return value.is_string() and value.get<std::string>() == "foo";
+            }));
+            CHECK(std::any_of(j_object.begin(), j_object.end(), [](const json & value)
+            {
+                return value.get<int>() > 1;
+            }));
+        }
+
+        SECTION("std::none_of")
+        {
+            CHECK(std::none_of(j_array.begin(), j_array.end(), [](const json & value)
+            {
+                return value.size() == 0;
+            }));
+            CHECK(std::none_of(j_object.begin(), j_object.end(), [](const json & value)
+            {
+                return value.get<int>() <= 0;
+            }));
+        }
+
+        SECTION("std::for_each")
+        {
+            SECTION("reading")
+            {
+                int sum = 0;
+
+                std::for_each(j_array.cbegin(), j_array.cend(), [&sum](const json & value)
+                {
+                    if (value.is_number())
+                    {
+                        sum += static_cast<int>(value);
+                    }
+                });
+
+                CHECK(sum == 45);
+            }
+
+            SECTION("writing")
+            {
+                auto add17 = [](json & value)
+                {
+                    if (value.is_array())
+                    {
+                        value.push_back(17);
+                    }
+                };
+
+                std::for_each(j_array.begin(), j_array.end(), add17);
+
+                CHECK(j_array[6] == json({1, 2, 3, 17}));
+            }
+        }
+
+        SECTION("std::count")
+        {
+            CHECK(std::count(j_array.begin(), j_array.end(), json(true)) == 1);
+        }
+
+        SECTION("std::count_if")
+        {
+            CHECK(std::count_if(j_array.begin(), j_array.end(), [](const json & value)
+            {
+                return (value.is_number());
+            }) == 3);
+            CHECK(std::count_if(j_array.begin(), j_array.end(), [](const json&)
+            {
+                return true;
+            }) == 9);
+        }
+
+        SECTION("std::mismatch")
+        {
+            json j_array2 = {13, 29, 3, {{"one", 1}, {"two", 2}, {"three", 3}}, true, false, {1, 2, 3}, "foo", "baz"};
+            auto res = std::mismatch(j_array.begin(), j_array.end(), j_array2.begin());
+            CHECK(*res.first == json({{"one", 1}, {"two", 2}}));
+            CHECK(*res.second == json({{"one", 1}, {"two", 2}, {"three", 3}}));
+        }
+
+        SECTION("std::equal")
+        {
+            SECTION("using operator==")
+            {
+                CHECK(std::equal(j_array.begin(), j_array.end(), j_array.begin()));
+                CHECK(std::equal(j_object.begin(), j_object.end(), j_object.begin()));
+                CHECK(not std::equal(j_array.begin(), j_array.end(), j_object.begin()));
+            }
+
+            SECTION("using user-defined comparison")
+            {
+                // compare objects only by size of its elements
+                json j_array2 = {13, 29, 3, {"Hello", "World"}, true, false, {{"one", 1}, {"two", 2}, {"three", 3}}, "foo", "baz"};
+                CHECK(not std::equal(j_array.begin(), j_array.end(), j_array2.begin()));
+                CHECK(std::equal(j_array.begin(), j_array.end(), j_array2.begin(),
+                                 [](const json & a, const json & b)
+                {
+                    return (a.size() == b.size());
+                }));
+            }
+        }
+
+        SECTION("std::find")
+        {
+            auto it = std::find(j_array.begin(), j_array.end(), json(false));
+            CHECK(std::distance(j_array.begin(), it) == 5);
+        }
+
+        SECTION("std::find_if")
+        {
+            auto it = std::find_if(j_array.begin(), j_array.end(),
+                                   [](const json & value)
+            {
+                return value.is_boolean();
+            });
+            CHECK(std::distance(j_array.begin(), it) == 4);
+        }
+
+        SECTION("std::find_if_not")
+        {
+            auto it = std::find_if_not(j_array.begin(), j_array.end(),
+                                       [](const json & value)
+            {
+                return value.is_number();
+            });
+            CHECK(std::distance(j_array.begin(), it) == 3);
+        }
+
+        SECTION("std::adjacent_find")
+        {
+            CHECK(std::adjacent_find(j_array.begin(), j_array.end()) == j_array.end());
+            CHECK(std::adjacent_find(j_array.begin(), j_array.end(),
+                                     [](const json & v1, const json & v2)
+            {
+                return v1.type() == v2.type();
+            }) == j_array.begin());
+        }
+    }
+
+    SECTION("modifying sequence operations")
+    {
+        SECTION("std::reverse")
+        {
+            std::reverse(j_array.begin(), j_array.end());
+            CHECK(j_array == json({"baz", "foo", {1, 2, 3}, false, true, {{"one", 1}, {"two", 2}}, 3, 29, 13}));
+        }
+
+        SECTION("std::rotate")
+        {
+            std::rotate(j_array.begin(), j_array.begin() + 1, j_array.end());
+            CHECK(j_array == json({29, 3, {{"one", 1}, {"two", 2}}, true, false, {1, 2, 3}, "foo", "baz", 13}));
+        }
+
+        SECTION("std::partition")
+        {
+            auto it = std::partition(j_array.begin(), j_array.end(), [](const json & v)
+            {
+                return v.is_string();
+            });
+            CHECK(std::distance(j_array.begin(), it) == 2);
+            CHECK(not it[2].is_string());
+        }
+    }
+
+    SECTION("sorting operations")
+    {
+        SECTION("std::sort")
+        {
+            SECTION("with standard comparison")
+            {
+                json j = {13, 29, 3, {{"one", 1}, {"two", 2}}, true, false, {1, 2, 3}, "foo", "baz", nullptr};
+                std::sort(j.begin(), j.end());
+                CHECK(j == json({nullptr, false, true, 3, 13, 29, {{"one", 1}, {"two", 2}}, {1, 2, 3}, "baz", "foo"}));
+            }
+
+            SECTION("with user-defined comparison")
+            {
+                json j = {3, {{"one", 1}, {"two", 2}}, {1, 2, 3}, nullptr};
+                std::sort(j.begin(), j.end(), [](const json & a, const json & b)
+                {
+                    return a.size() < b.size();
+                });
+                CHECK(j == json({nullptr, 3, {{"one", 1}, {"two", 2}}, {1, 2, 3}}));
+            }
+
+            SECTION("sorting an object")
+            {
+                json j({{"one", 1}, {"two", 2}});
+                CHECK_THROWS_AS(std::sort(j.begin(), j.end()), std::domain_error);
+                CHECK_THROWS_WITH(std::sort(j.begin(), j.end()), "cannot use offsets with object iterators");
+            }
+        }
+
+        SECTION("std::partial_sort")
+        {
+            json j = {13, 29, 3, {{"one", 1}, {"two", 2}}, true, false, {1, 2, 3}, "foo", "baz", nullptr};
+            std::partial_sort(j.begin(), j.begin() + 4, j.end());
+            CHECK(j == json({nullptr, false, true, 3, {{"one", 1}, {"two", 2}}, 29, {1, 2, 3}, "foo", "baz", 13}));
+        }
+    }
+
+    SECTION("set operations")
+    {
+        SECTION("std::merge")
+        {
+            {
+                json j1 = {2, 4, 6, 8};
+                json j2 = {1, 2, 3, 5, 7};
+                json j3;
+
+                std::merge(j1.begin(), j1.end(), j2.begin(), j2.end(), std::back_inserter(j3));
+                CHECK(j3 == json({1, 2, 2, 3, 4, 5, 6, 7, 8}));
+            }
+        }
+
+        SECTION("std::set_difference")
+        {
+            json j1 = {1, 2, 3, 4, 5, 6, 7, 8};
+            json j2 = {1, 2, 3, 5, 7};
+            json j3;
+
+            std::set_difference(j1.begin(), j1.end(), j2.begin(), j2.end(), std::back_inserter(j3));
+            CHECK(j3 == json({4, 6, 8}));
+        }
+
+        SECTION("std::set_intersection")
+        {
+            json j1 = {1, 2, 3, 4, 5, 6, 7, 8};
+            json j2 = {1, 2, 3, 5, 7};
+            json j3;
+
+            std::set_intersection(j1.begin(), j1.end(), j2.begin(), j2.end(), std::back_inserter(j3));
+            CHECK(j3 == json({1, 2, 3, 5, 7}));
+        }
+
+        SECTION("std::set_union")
+        {
+            json j1 = {2, 4, 6, 8};
+            json j2 = {1, 2, 3, 5, 7};
+            json j3;
+
+            std::set_union(j1.begin(), j1.end(), j2.begin(), j2.end(), std::back_inserter(j3));
+            CHECK(j3 == json({1, 2, 3, 4, 5, 6, 7, 8}));
+        }
+
+        SECTION("std::set_symmetric_difference")
+        {
+            json j1 = {2, 4, 6, 8};
+            json j2 = {1, 2, 3, 5, 7};
+            json j3;
+
+            std::set_symmetric_difference(j1.begin(), j1.end(), j2.begin(), j2.end(), std::back_inserter(j3));
+            CHECK(j3 == json({1, 3, 4, 5, 6, 7, 8}));
+        }
+    }
+
+    SECTION("heap operations")
+    {
+        std::make_heap(j_array.begin(), j_array.end());
+        CHECK(std::is_heap(j_array.begin(), j_array.end()));
+        std::sort_heap(j_array.begin(), j_array.end());
+        CHECK(j_array == json({false, true, 3, 13, 29, {{"one", 1}, {"two", 2}}, {1, 2, 3}, "baz", "foo"}));
+    }
+}

test/src/unit-allocator.cpp

@@ -0,0 +1,234 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+// special test case to check if memory is leaked if constructor throws
+
+template<class T>
+struct bad_allocator : std::allocator<T>
+{
+    template<class... Args>
+    void construct(T*, Args&& ...)
+    {
+        throw std::bad_alloc();
+    }
+};
+
+TEST_CASE("bad_alloc")
+{
+    SECTION("bad_alloc")
+    {
+        // create JSON type using the throwing allocator
+        using bad_json = nlohmann::basic_json<std::map,
+              std::vector,
+              std::string,
+              bool,
+              std::int64_t,
+              std::uint64_t,
+              double,
+              bad_allocator>;
+
+        // creating an object should throw
+        CHECK_THROWS_AS(bad_json j(bad_json::value_t::object), std::bad_alloc);
+    }
+}
+
+bool next_construct_fails = false;
+bool next_destroy_fails = false;
+bool next_deallocate_fails = false;
+
+template<class T>
+struct my_allocator : std::allocator<T>
+{
+    template<class... Args>
+    void construct(T* p, Args&& ... args)
+    {
+        if (next_construct_fails)
+        {
+            next_construct_fails = false;
+            throw std::bad_alloc();
+        }
+        else
+        {
+            ::new(reinterpret_cast<void*>(p)) T(std::forward<Args>(args)...);
+        }
+    }
+
+    void deallocate(T* p, std::size_t n)
+    {
+        if (next_deallocate_fails)
+        {
+            next_deallocate_fails = false;
+            throw std::bad_alloc();
+        }
+        else
+        {
+            std::allocator<T>::deallocate(p, n);
+        }
+    }
+
+    void destroy(T* p)
+    {
+        if (next_destroy_fails)
+        {
+            next_destroy_fails = false;
+            throw std::bad_alloc();
+        }
+        else
+        {
+            p->~T();
+        }
+    }
+};
+
+TEST_CASE("controlled bad_alloc")
+{
+    // create JSON type using the throwing allocator
+    using my_json = nlohmann::basic_json<std::map,
+          std::vector,
+          std::string,
+          bool,
+          std::int64_t,
+          std::uint64_t,
+          double,
+          my_allocator>;
+
+    SECTION("class json_value")
+    {
+        SECTION("json_value(value_t)")
+        {
+            SECTION("object")
+            {
+                next_construct_fails = false;
+                auto t = my_json::value_t::object;
+                CHECK_NOTHROW(my_json::json_value j(t));
+                next_construct_fails = true;
+                CHECK_THROWS_AS(my_json::json_value j(t), std::bad_alloc);
+                next_construct_fails = false;
+            }
+            SECTION("array")
+            {
+                next_construct_fails = false;
+                auto t = my_json::value_t::array;
+                CHECK_NOTHROW(my_json::json_value j(t));
+                next_construct_fails = true;
+                CHECK_THROWS_AS(my_json::json_value j(t), std::bad_alloc);
+                next_construct_fails = false;
+            }
+            SECTION("string")
+            {
+                next_construct_fails = false;
+                auto t = my_json::value_t::string;
+                CHECK_NOTHROW(my_json::json_value j(t));
+                next_construct_fails = true;
+                CHECK_THROWS_AS(my_json::json_value j(t), std::bad_alloc);
+                next_construct_fails = false;
+            }
+        }
+
+        SECTION("json_value(const string_t&)")
+        {
+            next_construct_fails = false;
+            my_json::string_t v("foo");
+            CHECK_NOTHROW(my_json::json_value j(v));
+            next_construct_fails = true;
+            CHECK_THROWS_AS(my_json::json_value j(v), std::bad_alloc);
+            next_construct_fails = false;
+        }
+
+        /*
+                SECTION("json_value(const object_t&)")
+                {
+                    next_construct_fails = false;
+                    my_json::object_t v {{"foo", "bar"}};
+                    CHECK_NOTHROW(my_json::json_value j(v));
+                    next_construct_fails = true;
+                    CHECK_THROWS_AS(my_json::json_value j(v), std::bad_alloc);
+                    next_construct_fails = false;
+                }
+        */
+        /*
+                SECTION("json_value(const array_t&)")
+                {
+                    next_construct_fails = false;
+                    my_json::array_t v = {"foo", "bar", "baz"};
+                    CHECK_NOTHROW(my_json::json_value j(v));
+                    next_construct_fails = true;
+                    CHECK_THROWS_AS(my_json::json_value j(v), std::bad_alloc);
+                    next_construct_fails = false;
+                }
+        */
+    }
+
+    SECTION("class basic_json")
+    {
+        SECTION("basic_json(const CompatibleObjectType&)")
+        {
+            next_construct_fails = false;
+            std::map<std::string, std::string> v {{"foo", "bar"}};
+            CHECK_NOTHROW(my_json j(v));
+            next_construct_fails = true;
+            CHECK_THROWS_AS(my_json j(v), std::bad_alloc);
+            next_construct_fails = false;
+        }
+
+        SECTION("basic_json(const CompatibleArrayType&)")
+        {
+            next_construct_fails = false;
+            std::vector<std::string> v {"foo", "bar", "baz"};
+            CHECK_NOTHROW(my_json j(v));
+            next_construct_fails = true;
+            CHECK_THROWS_AS(my_json j(v), std::bad_alloc);
+            next_construct_fails = false;
+        }
+
+        SECTION("basic_json(const typename string_t::value_type*)")
+        {
+            next_construct_fails = false;
+            CHECK_NOTHROW(my_json v("foo"));
+            next_construct_fails = true;
+            CHECK_THROWS_AS(my_json v("foo"), std::bad_alloc);
+            next_construct_fails = false;
+        }
+
+        SECTION("basic_json(const typename string_t::value_type*)")
+        {
+            next_construct_fails = false;
+            std::string s("foo");
+            CHECK_NOTHROW(my_json v(s));
+            next_construct_fails = true;
+            CHECK_THROWS_AS(my_json v(s), std::bad_alloc);
+            next_construct_fails = false;
+        }
+    }
+}

test/src/unit-capacity.cpp

@@ -0,0 +1,562 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("capacity")
+{
+    SECTION("empty()")
+    {
+        SECTION("boolean")
+        {
+            json j = true;
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == false);
+                CHECK(j_const.empty() == false);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+
+        SECTION("string")
+        {
+            json j = "hello world";
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == false);
+                CHECK(j_const.empty() == false);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+
+        SECTION("array")
+        {
+            SECTION("empty array")
+            {
+                json j = json::array();
+                json j_const(j);
+
+                SECTION("result of empty")
+                {
+                    CHECK(j.empty() == true);
+                    CHECK(j_const.empty() == true);
+                }
+
+                SECTION("definition of empty")
+                {
+                    CHECK(j.empty() == (j.begin() == j.end()));
+                    CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+                }
+            }
+
+            SECTION("filled array")
+            {
+                json j = {1, 2, 3};
+                json j_const(j);
+
+                SECTION("result of empty")
+                {
+                    CHECK(j.empty() == false);
+                    CHECK(j_const.empty() == false);
+                }
+
+                SECTION("definition of empty")
+                {
+                    CHECK(j.empty() == (j.begin() == j.end()));
+                    CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+                }
+            }
+        }
+
+        SECTION("object")
+        {
+            SECTION("empty object")
+            {
+                json j = json::object();
+                json j_const(j);
+
+                SECTION("result of empty")
+                {
+                    CHECK(j.empty() == true);
+                    CHECK(j_const.empty() == true);
+                }
+
+                SECTION("definition of empty")
+                {
+                    CHECK(j.empty() == (j.begin() == j.end()));
+                    CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+                }
+            }
+
+            SECTION("filled object")
+            {
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j_const(j);
+
+                SECTION("result of empty")
+                {
+                    CHECK(j.empty() == false);
+                    CHECK(j_const.empty() == false);
+                }
+
+                SECTION("definition of empty")
+                {
+                    CHECK(j.empty() == (j.begin() == j.end()));
+                    CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+                }
+            }
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == false);
+                CHECK(j_const.empty() == false);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == false);
+                CHECK(j_const.empty() == false);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+
+        SECTION("number (float)")
+        {
+            json j = 23.42;
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == false);
+                CHECK(j_const.empty() == false);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+
+        SECTION("null")
+        {
+            json j = nullptr;
+            json j_const(j);
+
+            SECTION("result of empty")
+            {
+                CHECK(j.empty() == true);
+                CHECK(j_const.empty() == true);
+            }
+
+            SECTION("definition of empty")
+            {
+                CHECK(j.empty() == (j.begin() == j.end()));
+                CHECK(j_const.empty() == (j_const.begin() == j_const.end()));
+            }
+        }
+    }
+
+    SECTION("size()")
+    {
+        SECTION("boolean")
+        {
+            json j = true;
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 1);
+                CHECK(j_const.size() == 1);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+
+        SECTION("string")
+        {
+            json j = "hello world";
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 1);
+                CHECK(j_const.size() == 1);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+
+        SECTION("array")
+        {
+            SECTION("empty array")
+            {
+                json j = json::array();
+                json j_const(j);
+
+                SECTION("result of size")
+                {
+                    CHECK(j.size() == 0);
+                    CHECK(j_const.size() == 0);
+                }
+
+                SECTION("definition of size")
+                {
+                    CHECK(std::distance(j.begin(), j.end()) == j.size());
+                    CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                    CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                    CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+                }
+            }
+
+            SECTION("filled array")
+            {
+                json j = {1, 2, 3};
+                json j_const(j);
+
+                SECTION("result of size")
+                {
+                    CHECK(j.size() == 3);
+                    CHECK(j_const.size() == 3);
+                }
+
+                SECTION("definition of size")
+                {
+                    CHECK(std::distance(j.begin(), j.end()) == j.size());
+                    CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                    CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                    CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+                }
+            }
+        }
+
+        SECTION("object")
+        {
+            SECTION("empty object")
+            {
+                json j = json::object();
+                json j_const(j);
+
+                SECTION("result of size")
+                {
+                    CHECK(j.size() == 0);
+                    CHECK(j_const.size() == 0);
+                }
+
+                SECTION("definition of size")
+                {
+                    CHECK(std::distance(j.begin(), j.end()) == j.size());
+                    CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                    CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                    CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+                }
+            }
+
+            SECTION("filled object")
+            {
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j_const(j);
+
+                SECTION("result of size")
+                {
+                    CHECK(j.size() == 3);
+                    CHECK(j_const.size() == 3);
+                }
+
+                SECTION("definition of size")
+                {
+                    CHECK(std::distance(j.begin(), j.end()) == j.size());
+                    CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                    CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                    CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+                }
+            }
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 1);
+                CHECK(j_const.size() == 1);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 1);
+                CHECK(j_const.size() == 1);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+
+        SECTION("number (float)")
+        {
+            json j = 23.42;
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 1);
+                CHECK(j_const.size() == 1);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+
+        SECTION("null")
+        {
+            json j = nullptr;
+            json j_const(j);
+
+            SECTION("result of size")
+            {
+                CHECK(j.size() == 0);
+                CHECK(j_const.size() == 0);
+            }
+
+            SECTION("definition of size")
+            {
+                CHECK(std::distance(j.begin(), j.end()) == j.size());
+                CHECK(std::distance(j_const.begin(), j_const.end()) == j_const.size());
+                CHECK(std::distance(j.rbegin(), j.rend()) == j.size());
+                CHECK(std::distance(j_const.crbegin(), j_const.crend()) == j_const.size());
+            }
+        }
+    }
+
+    SECTION("max_size()")
+    {
+        SECTION("boolean")
+        {
+            json j = true;
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 1);
+                CHECK(j_const.max_size() == 1);
+            }
+        }
+
+        SECTION("string")
+        {
+            json j = "hello world";
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 1);
+                CHECK(j_const.max_size() == 1);
+            }
+        }
+
+        SECTION("array")
+        {
+            SECTION("empty array")
+            {
+                json j = json::array();
+                json j_const(j);
+
+                SECTION("result of max_size")
+                {
+                    CHECK(j.max_size() >= j.size());
+                    CHECK(j_const.max_size() >= j_const.size());
+                }
+            }
+
+            SECTION("filled array")
+            {
+                json j = {1, 2, 3};
+                json j_const(j);
+
+                SECTION("result of max_size")
+                {
+                    CHECK(j.max_size() >= j.size());
+                    CHECK(j_const.max_size() >= j_const.size());
+                }
+            }
+        }
+
+        SECTION("object")
+        {
+            SECTION("empty object")
+            {
+                json j = json::object();
+                json j_const(j);
+
+                SECTION("result of max_size")
+                {
+                    CHECK(j.max_size() >= j.size());
+                    CHECK(j_const.max_size() >= j_const.size());
+                }
+            }
+
+            SECTION("filled object")
+            {
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j_const(j);
+
+                SECTION("result of max_size")
+                {
+                    CHECK(j.max_size() >= j.size());
+                    CHECK(j_const.max_size() >= j_const.size());
+                }
+            }
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 1);
+                CHECK(j_const.max_size() == 1);
+            }
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 1);
+                CHECK(j_const.max_size() == 1);
+            }
+        }
+
+        SECTION("number (float)")
+        {
+            json j = 23.42;
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 1);
+                CHECK(j_const.max_size() == 1);
+            }
+        }
+
+        SECTION("null")
+        {
+            json j = nullptr;
+            json j_const(j);
+
+            SECTION("result of max_size")
+            {
+                CHECK(j.max_size() == 0);
+                CHECK(j_const.max_size() == 0);
+            }
+        }
+    }
+}

test/src/unit-class_const_iterator.cpp

@@ -0,0 +1,401 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("const_iterator class")
+{
+    SECTION("construction")
+    {
+        SECTION("constructor")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it(&j);
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::const_iterator it(&j);
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::const_iterator it(&j);
+            }
+        }
+
+        SECTION("copy assignment")
+        {
+            json j(json::value_t::null);
+            json::const_iterator it(&j);
+            json::const_iterator it2(&j);
+            it2 = it;
+        }
+    }
+
+    SECTION("initialization")
+    {
+        SECTION("set_begin")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.cbegin());
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::const_iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.cbegin());
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::const_iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.cbegin());
+            }
+        }
+
+        SECTION("set_end")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it(&j);
+                it.set_end();
+                CHECK(it == j.cend());
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::const_iterator it(&j);
+                it.set_end();
+                CHECK(it == j.cend());
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::const_iterator it(&j);
+                it.set_end();
+                CHECK(it == j.cend());
+            }
+        }
+    }
+
+    SECTION("element access")
+    {
+        SECTION("operator*")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cbegin();
+                CHECK_THROWS_AS(*it, std::out_of_range);
+                CHECK_THROWS_WITH(*it, "cannot get value");
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cbegin();
+                CHECK(*it == json(17));
+                it = j.cend();
+                CHECK_THROWS_AS(*it, std::out_of_range);
+                CHECK_THROWS_WITH(*it, "cannot get value");
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cbegin();
+                CHECK(*it == json("bar"));
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cbegin();
+                CHECK(*it == json(1));
+            }
+        }
+
+        SECTION("operator->")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cbegin();
+                CHECK_THROWS_AS(it->type_name(), std::out_of_range);
+                CHECK_THROWS_WITH(it->type_name(), "cannot get value");
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cbegin();
+                CHECK(it->type_name() == "number");
+                it = j.cend();
+                CHECK_THROWS_AS(it->type_name(), std::out_of_range);
+                CHECK_THROWS_WITH(it->type_name(), "cannot get value");
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cbegin();
+                CHECK(it->type_name() == "string");
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cbegin();
+                CHECK(it->type_name() == "number");
+            }
+        }
+    }
+
+    SECTION("increment/decrement")
+    {
+        SECTION("post-increment")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.primitive_iterator == 1);
+                it++;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.primitive_iterator == 0);
+                it++;
+                CHECK(it.m_it.primitive_iterator == 1);
+                it++;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+                it++;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("pre-increment")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.primitive_iterator == 1);
+                ++it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.primitive_iterator == 0);
+                ++it;
+                CHECK(it.m_it.primitive_iterator == 1);
+                ++it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+                ++it;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cbegin();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("post-decrement")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.primitive_iterator == 1);
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.primitive_iterator == 1);
+                it--;
+                CHECK(it.m_it.primitive_iterator == 0);
+                it--;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+                it--;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("pre-decrement")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.primitive_iterator == 1);
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.primitive_iterator == 1);
+                --it;
+                CHECK(it.m_it.primitive_iterator == 0);
+                --it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+                --it;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::const_iterator it = j.cend();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+            }
+        }
+    }
+}

test/src/unit-class_iterator.cpp

@@ -0,0 +1,401 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("iterator class")
+{
+    SECTION("construction")
+    {
+        SECTION("constructor")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it(&j);
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::iterator it(&j);
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::iterator it(&j);
+            }
+        }
+
+        SECTION("copy assignment")
+        {
+            json j(json::value_t::null);
+            json::iterator it(&j);
+            json::iterator it2(&j);
+            it2 = it;
+        }
+    }
+
+    SECTION("initialization")
+    {
+        SECTION("set_begin")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.begin());
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.begin());
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::iterator it(&j);
+                it.set_begin();
+                CHECK(it == j.begin());
+            }
+        }
+
+        SECTION("set_end")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it(&j);
+                it.set_end();
+                CHECK(it == j.end());
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                json::iterator it(&j);
+                it.set_end();
+                CHECK(it == j.end());
+            }
+
+            SECTION("array")
+            {
+                json j(json::value_t::array);
+                json::iterator it(&j);
+                it.set_end();
+                CHECK(it == j.end());
+            }
+        }
+    }
+
+    SECTION("element access")
+    {
+        SECTION("operator*")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.begin();
+                CHECK_THROWS_AS(*it, std::out_of_range);
+                CHECK_THROWS_WITH(*it, "cannot get value");
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.begin();
+                CHECK(*it == json(17));
+                it = j.end();
+                CHECK_THROWS_AS(*it, std::out_of_range);
+                CHECK_THROWS_WITH(*it, "cannot get value");
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.begin();
+                CHECK(*it == json("bar"));
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.begin();
+                CHECK(*it == json(1));
+            }
+        }
+
+        SECTION("operator->")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.begin();
+                CHECK_THROWS_AS(it->type_name(), std::out_of_range);
+                CHECK_THROWS_WITH(it->type_name(), "cannot get value");
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.begin();
+                CHECK(it->type_name() == "number");
+                it = j.end();
+                CHECK_THROWS_AS(it->type_name(), std::out_of_range);
+                CHECK_THROWS_WITH(it->type_name(), "cannot get value");
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.begin();
+                CHECK(it->type_name() == "string");
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.begin();
+                CHECK(it->type_name() == "number");
+            }
+        }
+    }
+
+    SECTION("increment/decrement")
+    {
+        SECTION("post-increment")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.begin();
+                CHECK(it.m_it.primitive_iterator == 1);
+                it++;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.begin();
+                CHECK(it.m_it.primitive_iterator == 0);
+                it++;
+                CHECK(it.m_it.primitive_iterator == 1);
+                it++;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.begin();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+                it++;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.begin();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it++;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("pre-increment")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.begin();
+                CHECK(it.m_it.primitive_iterator == 1);
+                ++it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.begin();
+                CHECK(it.m_it.primitive_iterator == 0);
+                ++it;
+                CHECK(it.m_it.primitive_iterator == 1);
+                ++it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.begin();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+                ++it;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.begin();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                ++it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("post-decrement")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.end();
+                CHECK(it.m_it.primitive_iterator == 1);
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.end();
+                CHECK(it.m_it.primitive_iterator == 1);
+                it--;
+                CHECK(it.m_it.primitive_iterator == 0);
+                it--;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.end();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+                it--;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.end();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                it--;
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+            }
+        }
+
+        SECTION("pre-decrement")
+        {
+            SECTION("null")
+            {
+                json j(json::value_t::null);
+                json::iterator it = j.end();
+                CHECK(it.m_it.primitive_iterator == 1);
+            }
+
+            SECTION("number")
+            {
+                json j(17);
+                json::iterator it = j.end();
+                CHECK(it.m_it.primitive_iterator == 1);
+                --it;
+                CHECK(it.m_it.primitive_iterator == 0);
+                --it;
+                CHECK((it.m_it.primitive_iterator != 0 and it.m_it.primitive_iterator != 1));
+            }
+
+            SECTION("object")
+            {
+                json j({{"foo", "bar"}});
+                json::iterator it = j.end();
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->end());
+                --it;
+                CHECK(it.m_it.object_iterator == it.m_object->m_value.object->begin());
+            }
+
+            SECTION("array")
+            {
+                json j({1, 2, 3, 4});
+                json::iterator it = j.end();
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+                --it;
+                CHECK(it.m_it.array_iterator == it.m_object->m_value.array->begin());
+                CHECK(it.m_it.array_iterator != it.m_object->m_value.array->end());
+            }
+        }
+    }
+}

test/src/unit-class_lexer.cpp

@@ -0,0 +1,155 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("lexer class")
+{
+    SECTION("scan")
+    {
+        SECTION("structural characters")
+        {
+            CHECK(json::lexer("[").scan() == json::lexer::token_type::begin_array);
+            CHECK(json::lexer("]").scan() == json::lexer::token_type::end_array);
+            CHECK(json::lexer("{").scan() == json::lexer::token_type::begin_object);
+            CHECK(json::lexer("}").scan() == json::lexer::token_type::end_object);
+            CHECK(json::lexer(",").scan() == json::lexer::token_type::value_separator);
+            CHECK(json::lexer(":").scan() == json::lexer::token_type::name_separator);
+        }
+
+        SECTION("literal names")
+        {
+            CHECK(json::lexer("null").scan() == json::lexer::token_type::literal_null);
+            CHECK(json::lexer("true").scan() == json::lexer::token_type::literal_true);
+            CHECK(json::lexer("false").scan() == json::lexer::token_type::literal_false);
+        }
+
+        SECTION("numbers")
+        {
+            CHECK(json::lexer("0").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("1").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("2").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("3").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("4").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("5").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("6").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("7").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("8").scan() == json::lexer::token_type::value_number);
+            CHECK(json::lexer("9").scan() == json::lexer::token_type::value_number);
+        }
+
+        SECTION("whitespace")
+        {
+            // result is end_of_input, because not token is following
+            CHECK(json::lexer(" ").scan() == json::lexer::token_type::end_of_input);
+            CHECK(json::lexer("\t").scan() == json::lexer::token_type::end_of_input);
+            CHECK(json::lexer("\n").scan() == json::lexer::token_type::end_of_input);
+            CHECK(json::lexer("\r").scan() == json::lexer::token_type::end_of_input);
+            CHECK(json::lexer(" \t\n\r\n\t ").scan() == json::lexer::token_type::end_of_input);
+        }
+    }
+
+    SECTION("token_type_name")
+    {
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::uninitialized) == "<uninitialized>");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::literal_true) == "true literal");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::literal_false) == "false literal");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::literal_null) == "null literal");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::value_string) == "string literal");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::value_number) == "number literal");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::begin_array) == "'['");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::begin_object) == "'{'");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::end_array) == "']'");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::end_object) == "'}'");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::name_separator) == "':'");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::value_separator) == "','");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::parse_error) == "<parse error>");
+        CHECK(json::lexer::token_type_name(json::lexer::token_type::end_of_input) == "end of input");
+    }
+
+    SECTION("parse errors on first character")
+    {
+        for (int c = 1; c < 128; ++c)
+        {
+            auto s = std::string(1, c);
+
+            switch (c)
+            {
+                // single characters that are valid tokens
+                case ('['):
+                case (']'):
+                case ('{'):
+                case ('}'):
+                case (','):
+                case (':'):
+                case ('0'):
+                case ('1'):
+                case ('2'):
+                case ('3'):
+                case ('4'):
+                case ('5'):
+                case ('6'):
+                case ('7'):
+                case ('8'):
+                case ('9'):
+                {
+                    CHECK(json::lexer(s.c_str()).scan() != json::lexer::token_type::parse_error);
+                    break;
+                }
+
+                // whitespace
+                case (' '):
+                case ('\t'):
+                case ('\n'):
+                case ('\r'):
+                {
+                    CHECK(json::lexer(s.c_str()).scan() == json::lexer::token_type::end_of_input);
+                    break;
+                }
+
+                // anything else is not expected
+                default:
+                {
+                    CHECK(json::lexer(s.c_str()).scan() == json::lexer::token_type::parse_error);
+                    break;
+                }
+            }
+        }
+    }
+
+    SECTION("to_unicode")
+    {
+        CHECK(json::lexer::to_unicode(0x1F4A9) == "💩");
+        CHECK_THROWS_AS(json::lexer::to_unicode(0x200000), std::out_of_range);
+        CHECK_THROWS_WITH(json::lexer::to_unicode(0x200000), "code points above 0x10FFFF are invalid");
+    }
+}

test/src/unit-class_parser.cpp

@@ -0,0 +1,765 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("parser class")
+{
+    SECTION("parse")
+    {
+        SECTION("null")
+        {
+            CHECK(json::parser("null").parse() == json(nullptr));
+        }
+
+        SECTION("true")
+        {
+            CHECK(json::parser("true").parse() == json(true));
+        }
+
+        SECTION("false")
+        {
+            CHECK(json::parser("false").parse() == json(false));
+        }
+
+        SECTION("array")
+        {
+            SECTION("empty array")
+            {
+                CHECK(json::parser("[]").parse() == json(json::value_t::array));
+                CHECK(json::parser("[ ]").parse() == json(json::value_t::array));
+            }
+
+            SECTION("nonempty array")
+            {
+                CHECK(json::parser("[true, false, null]").parse() == json({true, false, nullptr}));
+            }
+        }
+
+        SECTION("object")
+        {
+            SECTION("empty object")
+            {
+                CHECK(json::parser("{}").parse() == json(json::value_t::object));
+                CHECK(json::parser("{ }").parse() == json(json::value_t::object));
+            }
+
+            SECTION("nonempty object")
+            {
+                CHECK(json::parser("{\"\": true, \"one\": 1, \"two\": null}").parse() == json({{"", true}, {"one", 1}, {"two", nullptr}}));
+            }
+        }
+
+        SECTION("string")
+        {
+            // empty string
+            CHECK(json::parser("\"\"").parse() == json(json::value_t::string));
+
+            SECTION("errors")
+            {
+                // error: tab in string
+                CHECK_THROWS_AS(json::parser("\"\t\"").parse(), std::invalid_argument);
+                CHECK_THROWS_WITH(json::parser("\"\t\"").parse(), "parse error - unexpected '\"'");
+                // error: newline in string
+                CHECK_THROWS_AS(json::parser("\"\n\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\r\"").parse(), std::invalid_argument);
+                CHECK_THROWS_WITH(json::parser("\"\n\"").parse(), "parse error - unexpected '\"'");
+                CHECK_THROWS_WITH(json::parser("\"\r\"").parse(), "parse error - unexpected '\"'");
+                // error: backspace in string
+                CHECK_THROWS_AS(json::parser("\"\b\"").parse(), std::invalid_argument);
+                CHECK_THROWS_WITH(json::parser("\"\b\"").parse(), "parse error - unexpected '\"'");
+                // improve code coverage
+                CHECK_THROWS_AS(json::parser("\uFF01").parse(), std::invalid_argument);
+                // unescaped control characters
+                CHECK_THROWS_AS(json::parser("\"\x00\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x01\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x02\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x03\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x04\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x05\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x06\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x07\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x08\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x09\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0a\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0b\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0c\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0d\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0e\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x0f\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x10\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x11\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x12\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x13\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x14\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x15\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x16\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x17\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x18\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x19\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1a\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1b\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1c\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1d\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1e\"").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("\"\x1f\"").parse(), std::invalid_argument);
+            }
+
+            SECTION("escaped")
+            {
+                // quotation mark "\""
+                auto r1 = R"("\"")"_json;
+                CHECK(json::parser("\"\\\"\"").parse() == r1);
+                // reverse solidus "\\"
+                auto r2 = R"("\\")"_json;
+                CHECK(json::parser("\"\\\\\"").parse() == r2);
+                // solidus
+                CHECK(json::parser("\"\\/\"").parse() == R"("/")"_json);
+                // backspace
+                CHECK(json::parser("\"\\b\"").parse() == json("\b"));
+                // formfeed
+                CHECK(json::parser("\"\\f\"").parse() == json("\f"));
+                // newline
+                CHECK(json::parser("\"\\n\"").parse() == json("\n"));
+                // carriage return
+                CHECK(json::parser("\"\\r\"").parse() == json("\r"));
+                // horizontal tab
+                CHECK(json::parser("\"\\t\"").parse() == json("\t"));
+
+                CHECK(json::parser("\"\\u0001\"").parse().get<json::string_t>() == "\x01");
+                CHECK(json::parser("\"\\u000a\"").parse().get<json::string_t>() == "\n");
+                CHECK(json::parser("\"\\u00b0\"").parse().get<json::string_t>() == "°");
+                CHECK(json::parser("\"\\u0c00\"").parse().get<json::string_t>() == "ఀ");
+                CHECK(json::parser("\"\\ud000\"").parse().get<json::string_t>() == "퀀");
+                CHECK(json::parser("\"\\u000E\"").parse().get<json::string_t>() == "\x0E");
+                CHECK(json::parser("\"\\u00F0\"").parse().get<json::string_t>() == "ð");
+                CHECK(json::parser("\"\\u0100\"").parse().get<json::string_t>() == "Ā");
+                CHECK(json::parser("\"\\u2000\"").parse().get<json::string_t>() == " ");
+                CHECK(json::parser("\"\\uFFFF\"").parse().get<json::string_t>() == "￿");
+                CHECK(json::parser("\"\\u20AC\"").parse().get<json::string_t>() == "€");
+                CHECK(json::parser("\"€\"").parse().get<json::string_t>() == "€");
+                CHECK(json::parser("\"🎈\"").parse().get<json::string_t>() == "🎈");
+
+                CHECK(json::parse("\"\\ud80c\\udc60\"").get<json::string_t>() == u8"\U00013060");
+                CHECK(json::parse("\"\\ud83c\\udf1e\"").get<json::string_t>() == "🌞");
+            }
+        }
+
+        SECTION("number")
+        {
+            SECTION("integers")
+            {
+                SECTION("without exponent")
+                {
+                    CHECK(json::parser("-128").parse() == json(-128));
+                    CHECK(json::parser("-0").parse() == json(-0));
+                    CHECK(json::parser("0").parse() == json(0));
+                    CHECK(json::parser("128").parse() == json(128));
+                }
+
+                SECTION("with exponent")
+                {
+                    CHECK(json::parser("0e1").parse() == json(0e1));
+                    CHECK(json::parser("0E1").parse() == json(0e1));
+
+                    CHECK(json::parser("10000E-4").parse() == json(10000e-4));
+                    CHECK(json::parser("10000E-3").parse() == json(10000e-3));
+                    CHECK(json::parser("10000E-2").parse() == json(10000e-2));
+                    CHECK(json::parser("10000E-1").parse() == json(10000e-1));
+                    CHECK(json::parser("10000E0").parse() == json(10000e0));
+                    CHECK(json::parser("10000E1").parse() == json(10000e1));
+                    CHECK(json::parser("10000E2").parse() == json(10000e2));
+                    CHECK(json::parser("10000E3").parse() == json(10000e3));
+                    CHECK(json::parser("10000E4").parse() == json(10000e4));
+
+                    CHECK(json::parser("10000e-4").parse() == json(10000e-4));
+                    CHECK(json::parser("10000e-3").parse() == json(10000e-3));
+                    CHECK(json::parser("10000e-2").parse() == json(10000e-2));
+                    CHECK(json::parser("10000e-1").parse() == json(10000e-1));
+                    CHECK(json::parser("10000e0").parse() == json(10000e0));
+                    CHECK(json::parser("10000e1").parse() == json(10000e1));
+                    CHECK(json::parser("10000e2").parse() == json(10000e2));
+                    CHECK(json::parser("10000e3").parse() == json(10000e3));
+                    CHECK(json::parser("10000e4").parse() == json(10000e4));
+
+                    CHECK(json::parser("-0e1").parse() == json(-0e1));
+                    CHECK(json::parser("-0E1").parse() == json(-0e1));
+                    CHECK(json::parser("-0E123").parse() == json(-0e123));
+                }
+
+                SECTION("edge cases")
+                {
+                    // From RFC7159, Section 6:
+                    // Note that when such software is used, numbers that are
+                    // integers and are in the range [-(2**53)+1, (2**53)-1]
+                    // are interoperable in the sense that implementations will
+                    // agree exactly on their numeric values.
+
+                    // -(2**53)+1
+                    CHECK(json::parser("-9007199254740991").parse().get<int64_t>() == -9007199254740991);
+                    // (2**53)-1
+                    CHECK(json::parser("9007199254740991").parse().get<int64_t>() == 9007199254740991);
+                }
+
+                SECTION("over the edge cases")  // issue #178 - Integer conversion to unsigned (incorrect handling of 64 bit integers)
+                {
+                    // While RFC7159, Section 6 specifies a preference for support
+                    // for ranges in range of IEEE 754-2008 binary64 (double precision)
+                    // this does not accommodate 64 bit integers without loss of accuracy.
+                    // As 64 bit integers are now widely used in software, it is desirable
+                    // to expand support to to the full 64 bit (signed and unsigned) range
+                    // i.e. -(2**63) -> (2**64)-1.
+
+                    // -(2**63)    ** Note: compilers see negative literals as negated positive numbers (hence the -1))
+                    CHECK(json::parser("-9223372036854775808").parse().get<int64_t>() == -9223372036854775807 - 1);
+                    // (2**63)-1
+                    CHECK(json::parser("9223372036854775807").parse().get<int64_t>() == 9223372036854775807);
+                    // (2**64)-1
+                    CHECK(json::parser("18446744073709551615").parse().get<uint64_t>() == 18446744073709551615u);
+                }
+            }
+
+            SECTION("floating-point")
+            {
+                SECTION("without exponent")
+                {
+                    CHECK(json::parser("-128.5").parse() == json(-128.5));
+                    CHECK(json::parser("0.999").parse() == json(0.999));
+                    CHECK(json::parser("128.5").parse() == json(128.5));
+                    CHECK(json::parser("-0.0").parse() == json(-0.0));
+                }
+
+                SECTION("with exponent")
+                {
+                    CHECK(json::parser("-128.5E3").parse() == json(-128.5E3));
+                    CHECK(json::parser("-128.5E-3").parse() == json(-128.5E-3));
+                    CHECK(json::parser("-0.0e1").parse() == json(-0.0e1));
+                    CHECK(json::parser("-0.0E1").parse() == json(-0.0e1));
+                }
+            }
+
+            SECTION("invalid numbers")
+            {
+                CHECK_THROWS_AS(json::parser("01").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("--1").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("1.").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("1E").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("1E-").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("1.E1").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-1E").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0E#").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0E-#").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0#").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0.0:").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0.0Z").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0E123:").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0e0-:").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0e-:").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("-0f").parse(), std::invalid_argument);
+
+                // numbers must not begin with "+"
+                CHECK_THROWS_AS(json::parser("+1").parse(), std::invalid_argument);
+                CHECK_THROWS_AS(json::parser("+0").parse(), std::invalid_argument);
+
+                CHECK_THROWS_WITH(json::parser("01").parse(),
+                                  "parse error - unexpected number literal; expected end of input");
+                CHECK_THROWS_WITH(json::parser("--1").parse(), "parse error - unexpected '-'");
+                CHECK_THROWS_WITH(json::parser("1.").parse(),
+                                  "parse error - unexpected '.'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("1E").parse(),
+                                  "parse error - unexpected 'E'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("1E-").parse(),
+                                  "parse error - unexpected 'E'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("1.E1").parse(),
+                                  "parse error - unexpected '.'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-1E").parse(),
+                                  "parse error - unexpected 'E'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0E#").parse(),
+                                  "parse error - unexpected 'E'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0E-#").parse(),
+                                  "parse error - unexpected 'E'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0#").parse(),
+                                  "parse error - unexpected '#'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0.0:").parse(),
+                                  "parse error - unexpected ':'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0.0Z").parse(),
+                                  "parse error - unexpected 'Z'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0E123:").parse(),
+                                  "parse error - unexpected ':'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0e0-:").parse(),
+                                  "parse error - unexpected '-'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0e-:").parse(),
+                                  "parse error - unexpected 'e'; expected end of input");
+                CHECK_THROWS_WITH(json::parser("-0f").parse(),
+                                  "parse error - unexpected 'f'; expected end of input");
+            }
+        }
+    }
+
+    SECTION("parse errors")
+    {
+        // unexpected end of number
+        CHECK_THROWS_AS(json::parser("0.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("-").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("--").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("-0.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("-.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("-:").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("0.:").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("e.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1e.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1e/").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1e:").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1E.").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1E/").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("1E:").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("0.").parse(),
+                          "parse error - unexpected '.'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("-").parse(), "parse error - unexpected '-'");
+        CHECK_THROWS_WITH(json::parser("--").parse(),
+                          "parse error - unexpected '-'");
+        CHECK_THROWS_WITH(json::parser("-0.").parse(),
+                          "parse error - unexpected '.'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("-.").parse(),
+                          "parse error - unexpected '-'");
+        CHECK_THROWS_WITH(json::parser("-:").parse(),
+                          "parse error - unexpected '-'");
+        CHECK_THROWS_WITH(json::parser("0.:").parse(),
+                          "parse error - unexpected '.'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("e.").parse(),
+                          "parse error - unexpected 'e'");
+        CHECK_THROWS_WITH(json::parser("1e.").parse(),
+                          "parse error - unexpected 'e'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("1e/").parse(),
+                          "parse error - unexpected 'e'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("1e:").parse(),
+                          "parse error - unexpected 'e'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("1E.").parse(),
+                          "parse error - unexpected 'E'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("1E/").parse(),
+                          "parse error - unexpected 'E'; expected end of input");
+        CHECK_THROWS_WITH(json::parser("1E:").parse(),
+                          "parse error - unexpected 'E'; expected end of input");
+
+        // unexpected end of null
+        CHECK_THROWS_AS(json::parser("n").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("nu").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("nul").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("n").parse(), "parse error - unexpected 'n'");
+        CHECK_THROWS_WITH(json::parser("nu").parse(),
+                          "parse error - unexpected 'n'");
+        CHECK_THROWS_WITH(json::parser("nul").parse(),
+                          "parse error - unexpected 'n'");
+
+        // unexpected end of true
+        CHECK_THROWS_AS(json::parser("t").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("tr").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("tru").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("t").parse(), "parse error - unexpected 't'");
+        CHECK_THROWS_WITH(json::parser("tr").parse(),
+                          "parse error - unexpected 't'");
+        CHECK_THROWS_WITH(json::parser("tru").parse(),
+                          "parse error - unexpected 't'");
+
+        // unexpected end of false
+        CHECK_THROWS_AS(json::parser("f").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("fa").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("fal").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("fals").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("f").parse(), "parse error - unexpected 'f'");
+        CHECK_THROWS_WITH(json::parser("fa").parse(),
+                          "parse error - unexpected 'f'");
+        CHECK_THROWS_WITH(json::parser("fal").parse(),
+                          "parse error - unexpected 'f'");
+        CHECK_THROWS_WITH(json::parser("fals").parse(),
+                          "parse error - unexpected 'f'");
+
+        // missing/unexpected end of array
+        CHECK_THROWS_AS(json::parser("[").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("[1").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("[1,").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("[1,]").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("]").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("[").parse(),
+                          "parse error - unexpected end of input");
+        CHECK_THROWS_WITH(json::parser("[1").parse(),
+                          "parse error - unexpected end of input; expected ']'");
+        CHECK_THROWS_WITH(json::parser("[1,").parse(),
+                          "parse error - unexpected end of input");
+        CHECK_THROWS_WITH(json::parser("[1,]").parse(),
+                          "parse error - unexpected ']'");
+        CHECK_THROWS_WITH(json::parser("]").parse(), "parse error - unexpected ']'");
+
+        // missing/unexpected end of object
+        CHECK_THROWS_AS(json::parser("{").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("{\"foo\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("{\"foo\":").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("{\"foo\":}").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("{\"foo\":1,}").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("}").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("{").parse(),
+                          "parse error - unexpected end of input; expected string literal");
+        CHECK_THROWS_WITH(json::parser("{\"foo\"").parse(),
+                          "parse error - unexpected end of input; expected ':'");
+        CHECK_THROWS_WITH(json::parser("{\"foo\":").parse(),
+                          "parse error - unexpected end of input");
+        CHECK_THROWS_WITH(json::parser("{\"foo\":}").parse(),
+                          "parse error - unexpected '}'");
+        CHECK_THROWS_WITH(json::parser("{\"foo\":1,}").parse(),
+                          "parse error - unexpected '}'; expected string literal");
+        CHECK_THROWS_WITH(json::parser("}").parse(), "parse error - unexpected '}'");
+
+        // missing/unexpected end of string
+        CHECK_THROWS_AS(json::parser("\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u0\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u01\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u012\"").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u0").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u01").parse(), std::invalid_argument);
+        CHECK_THROWS_AS(json::parser("\"\\u012").parse(), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parser("\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u0\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u01\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u012\"").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u0").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u01").parse(),
+                          "parse error - unexpected '\"'");
+        CHECK_THROWS_WITH(json::parser("\"\\u012").parse(),
+                          "parse error - unexpected '\"'");
+
+        // invalid escapes
+        for (int c = 1; c < 128; ++c)
+        {
+            auto s = std::string("\"\\") + std::string(1, c) + "\"";
+
+            switch (c)
+            {
+                // valid escapes
+                case ('"'):
+                case ('\\'):
+                case ('/'):
+                case ('b'):
+                case ('f'):
+                case ('n'):
+                case ('r'):
+                case ('t'):
+                {
+                    CHECK_NOTHROW(json::parser(s).parse());
+                    break;
+                }
+
+                // \u must be followed with four numbers, so we skip it here
+                case ('u'):
+                {
+                    break;
+                }
+
+                // any other combination of backslash and character is invalid
+                default:
+                {
+                    CHECK_THROWS_AS(json::parser(s).parse(), std::invalid_argument);
+                    CHECK_THROWS_WITH(json::parser(s).parse(), "parse error - unexpected '\"'");
+                    break;
+                }
+            }
+        }
+
+        // invalid \uxxxx escapes
+        {
+            // check whether character is a valid hex character
+            const auto valid = [](int c)
+            {
+                switch (c)
+                {
+                    case ('0'):
+                    case ('1'):
+                    case ('2'):
+                    case ('3'):
+                    case ('4'):
+                    case ('5'):
+                    case ('6'):
+                    case ('7'):
+                    case ('8'):
+                    case ('9'):
+                    case ('a'):
+                    case ('b'):
+                    case ('c'):
+                    case ('d'):
+                    case ('e'):
+                    case ('f'):
+                    case ('A'):
+                    case ('B'):
+                    case ('C'):
+                    case ('D'):
+                    case ('E'):
+                    case ('F'):
+                    {
+                        return true;
+                    }
+
+                    default:
+                    {
+                        return false;
+                    }
+                }
+            };
+
+            for (int c = 1; c < 128; ++c)
+            {
+                std::string s = "\"\\u";
+
+                // create a string with the iterated character at each position
+                auto s1 = s + "000" + std::string(1, c) + "\"";
+                auto s2 = s + "00" + std::string(1, c) + "0\"";
+                auto s3 = s + "0" + std::string(1, c) + "00\"";
+                auto s4 = s + std::string(1, c) + "000\"";
+
+                if (valid(c))
+                {
+                    CHECK_NOTHROW(json::parser(s1).parse());
+                    CHECK_NOTHROW(json::parser(s2).parse());
+                    CHECK_NOTHROW(json::parser(s3).parse());
+                    CHECK_NOTHROW(json::parser(s4).parse());
+                }
+                else
+                {
+                    CHECK_THROWS_AS(json::parser(s1).parse(), std::invalid_argument);
+                    CHECK_THROWS_AS(json::parser(s2).parse(), std::invalid_argument);
+                    CHECK_THROWS_AS(json::parser(s3).parse(), std::invalid_argument);
+                    CHECK_THROWS_AS(json::parser(s4).parse(), std::invalid_argument);
+
+                    CHECK_THROWS_WITH(json::parser(s1).parse(), "parse error - unexpected '\"'");
+                    CHECK_THROWS_WITH(json::parser(s2).parse(), "parse error - unexpected '\"'");
+                    CHECK_THROWS_WITH(json::parser(s3).parse(), "parse error - unexpected '\"'");
+                    CHECK_THROWS_WITH(json::parser(s4).parse(), "parse error - unexpected '\"'");
+                }
+            }
+        }
+
+        // missing part of a surrogate pair
+        CHECK_THROWS_AS(json::parse("\"\\uD80C\""), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parse("\"\\uD80C\""), "missing low surrogate");
+        // invalid surrogate pair
+        CHECK_THROWS_AS(json::parse("\"\\uD80C\\uD80C\""), std::invalid_argument);
+        CHECK_THROWS_AS(json::parse("\"\\uD80C\\u0000\""), std::invalid_argument);
+        CHECK_THROWS_AS(json::parse("\"\\uD80C\\uFFFF\""), std::invalid_argument);
+        CHECK_THROWS_WITH(json::parse("\"\\uD80C\\uD80C\""),
+                          "missing or wrong low surrogate");
+        CHECK_THROWS_WITH(json::parse("\"\\uD80C\\u0000\""),
+                          "missing or wrong low surrogate");
+        CHECK_THROWS_WITH(json::parse("\"\\uD80C\\uFFFF\""),
+                          "missing or wrong low surrogate");
+    }
+
+    SECTION("callback function")
+    {
+        auto s_object = R"(
+            {
+                "foo": 2,
+                "bar": {
+                    "baz": 1
+                }
+            }
+        )";
+
+        auto s_array = R"(
+            [1,2,[3,4,5],4,5]
+        )";
+
+        SECTION("filter nothing")
+        {
+            json j_object = json::parse(s_object, [](int, json::parse_event_t, const json&)
+            {
+                return true;
+            });
+
+            CHECK (j_object == json({{"foo", 2}, {"bar", {{"baz", 1}}}}));
+
+            json j_array = json::parse(s_array, [](int, json::parse_event_t, const json&)
+            {
+                return true;
+            });
+
+            CHECK (j_array == json({1, 2, {3, 4, 5}, 4, 5}));
+        }
+
+        SECTION("filter everything")
+        {
+            json j_object = json::parse(s_object, [](int, json::parse_event_t, const json&)
+            {
+                return false;
+            });
+
+            // the top-level object will be discarded, leaving a null
+            CHECK (j_object.is_null());
+
+            json j_array = json::parse(s_array, [](int, json::parse_event_t, const json&)
+            {
+                return false;
+            });
+
+            // the top-level array will be discarded, leaving a null
+            CHECK (j_array.is_null());
+        }
+
+        SECTION("filter specific element")
+        {
+            json j_object = json::parse(s_object, [](int, json::parse_event_t, const json & j)
+            {
+                // filter all number(2) elements
+                if (j == json(2))
+                {
+                    return false;
+                }
+                else
+                {
+                    return true;
+                }
+            });
+
+            CHECK (j_object == json({{"bar", {{"baz", 1}}}}));
+
+            json j_array = json::parse(s_array, [](int, json::parse_event_t, const json & j)
+            {
+                if (j == json(2))
+                {
+                    return false;
+                }
+                else
+                {
+                    return true;
+                }
+            });
+
+            CHECK (j_array == json({1, {3, 4, 5}, 4, 5}));
+        }
+
+        SECTION("filter specific events")
+        {
+            SECTION("first closing event")
+            {
+                {
+                    json j_object = json::parse(s_object, [](int, json::parse_event_t e, const json&)
+                    {
+                        static bool first = true;
+                        if (e == json::parse_event_t::object_end and first)
+                        {
+                            first = false;
+                            return false;
+                        }
+                        else
+                        {
+                            return true;
+                        }
+                    });
+
+                    // the first completed object will be discarded
+                    CHECK (j_object == json({{"foo", 2}}));
+                }
+
+                {
+                    json j_array = json::parse(s_array, [](int, json::parse_event_t e, const json&)
+                    {
+                        static bool first = true;
+                        if (e == json::parse_event_t::array_end and first)
+                        {
+                            first = false;
+                            return false;
+                        }
+                        else
+                        {
+                            return true;
+                        }
+                    });
+
+                    // the first completed array will be discarded
+                    CHECK (j_array == json({1, 2, 4, 5}));
+                }
+            }
+        }
+
+        SECTION("special cases")
+        {
+            // the following test cases cover the situation in which an empty
+            // object and array is discarded only after the closing character
+            // has been read
+
+            json j_empty_object = json::parse("{}", [](int, json::parse_event_t e, const json&)
+            {
+                if (e == json::parse_event_t::object_end)
+                {
+                    return false;
+                }
+                else
+                {
+                    return true;
+                }
+            });
+            CHECK(j_empty_object == json());
+
+            json j_empty_array = json::parse("[]", [](int, json::parse_event_t e, const json&)
+            {
+                if (e == json::parse_event_t::array_end)
+                {
+                    return false;
+                }
+                else
+                {
+                    return true;
+                }
+            });
+            CHECK(j_empty_array == json());
+        }
+    }
+
+    SECTION("copy constructor")
+    {
+        json::string_t* s = new json::string_t("[1,2,3,4]");
+        json::parser p(*s);
+        delete s;
+        CHECK(p.parse() == json({1, 2, 3, 4}));
+    }
+}

test/src/unit-comparison.cpp

@@ -0,0 +1,246 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("lexicographical comparison operators")
+{
+    SECTION("types")
+    {
+        std::vector<json::value_t> j_types =
+        {
+            json::value_t::null,
+            json::value_t::boolean,
+            json::value_t::number_integer,
+            json::value_t::number_unsigned,
+            json::value_t::number_float,
+            json::value_t::object,
+            json::value_t::array,
+            json::value_t::string
+        };
+
+        SECTION("comparison: less")
+        {
+            std::vector<std::vector<bool>> expected =
+            {
+                {false, true, true, true, true, true, true, true},
+                {false, false, true, true, true, true, true, true},
+                {false, false, false, false, false, true, true, true},
+                {false, false, false, false, false, true, true, true},
+                {false, false, false, false, false, true, true, true},
+                {false, false, false, false, false, false, true, true},
+                {false, false, false, false, false, false, false, true},
+                {false, false, false, false, false, false, false, false}
+            };
+
+            for (size_t i = 0; i < j_types.size(); ++i)
+            {
+                for (size_t j = 0; j < j_types.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check precomputed values
+                    CHECK(operator<(j_types[i], j_types[j]) == expected[i][j]);
+                }
+            }
+        }
+    }
+
+    SECTION("values")
+    {
+        json j_values =
+        {
+            nullptr, nullptr,
+            17, 42,
+            8u, 13u,
+            3.14159, 23.42,
+            "foo", "bar",
+            true, false,
+            {1, 2, 3}, {"one", "two", "three"},
+            {{"first", 1}, {"second", 2}}, {{"a", "A"}, {"b", {"B"}}}
+        };
+
+        SECTION("comparison: equal")
+        {
+            std::vector<std::vector<bool>> expected =
+            {
+                {true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false},
+                {true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false},
+                {false, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false},
+                {false, false, false, true, false, false, false, false, false, false, false, false, false, false, false, false},
+                {false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, false},
+                {false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false},
+                {false, false, false, false, false, false, true, false, false, false, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, true, false, false, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, true, false, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, false, true, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, false, false, true, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, false, false, false, true, false, false, false, false},
+                {false, false, false, false, false, false, false, false, false, false, false, false, true, false, false, false},
+                {false, false, false, false, false, false, false, false, false, false, false, false, false, true, false, false},
+                {false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, false},
+                {false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true}
+            };
+
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check precomputed values
+                    CHECK( (j_values[i] == j_values[j]) == expected[i][j] );
+                }
+            }
+
+            // comparison with discarded elements
+            json j_discarded(json::value_t::discarded);
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                CHECK( (j_values[i] == j_discarded) == false);
+                CHECK( (j_discarded == j_values[i]) == false);
+                CHECK( (j_discarded == j_discarded) == false);
+            }
+
+            // compare with null pointer
+            json j_null;
+            CHECK(j_null == nullptr);
+            CHECK(nullptr == j_null);
+        }
+
+        SECTION("comparison: not equal")
+        {
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check definition
+                    CHECK( (j_values[i] != j_values[j]) == not(j_values[i] == j_values[j]) );
+                }
+            }
+
+            // compare with null pointer
+            json j_null;
+            CHECK( (j_null != nullptr) == false);
+            CHECK( (nullptr != j_null) == false);
+            CHECK( (j_null != nullptr) == not(j_null == nullptr));
+            CHECK( (nullptr != j_null) == not(nullptr == j_null));
+        }
+
+        SECTION("comparison: less")
+        {
+            std::vector<std::vector<bool>> expected =
+            {
+                {false, false, true, true, true, true, true, true, true, true, true, true, true, true, true, true},
+                {false, false, true, true, true, true, true, true, true, true, true, true, true, true, true, true},
+                {false, false, false, true, false, false, false, true, true, true, false, false, true, true, true, true},
+                {false, false, false, false, false, false, false, false, true, true, false, false, true, true, true, true},
+                {false, false, true, true, false, true, false, true, true, true, false, false, true, true, true, true},
+                {false, false, true, true, false, false, false, true, true, true, false, false, true, true, true, true},
+                {false, false, true, true, true, true, false, true, true, true, false, false, true, true, true, true},
+                {false, false, false, true, false, false, false, false, true, true, false, false, true, true, true, true},
+                {false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, true, false, false, false, false, false, false, false},
+                {false, false, true, true, true, true, true, true, true, true, false, false, true, true, true, true},
+                {false, false, true, true, true, true, true, true, true, true, true, false, true, true, true, true},
+                {false, false, false, false, false, false, false, false, true, true, false, false, false, true, false, false},
+                {false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false},
+                {false, false, false, false, false, false, false, false, true, true, false, false, true, true, false, false},
+                {false, false, false, false, false, false, false, false, true, true, false, false, true, true, true, false}
+            };
+
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check precomputed values
+                    CHECK( (j_values[i] < j_values[j]) == expected[i][j] );
+                }
+            }
+
+            // comparison with discarded elements
+            json j_discarded(json::value_t::discarded);
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                CAPTURE(i);
+                CHECK( (j_values[i] < j_discarded) == false);
+                CHECK( (j_discarded < j_values[i]) == false);
+                CHECK( (j_discarded < j_discarded) == false);
+            }
+        }
+
+        SECTION("comparison: less than or equal equal")
+        {
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check definition
+                    CHECK( (j_values[i] <= j_values[j]) == not(j_values[j] < j_values[i]) );
+                }
+            }
+        }
+
+        SECTION("comparison: greater than")
+        {
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check definition
+                    CHECK( (j_values[i] > j_values[j]) == (j_values[j] < j_values[i]) );
+                }
+            }
+        }
+
+        SECTION("comparison: greater than or equal")
+        {
+            for (size_t i = 0; i < j_values.size(); ++i)
+            {
+                for (size_t j = 0; j < j_values.size(); ++j)
+                {
+                    CAPTURE(i);
+                    CAPTURE(j);
+                    // check definition
+                    CHECK( (j_values[i] >= j_values[j]) == not(j_values[i] < j_values[j]) );
+                }
+            }
+        }
+    }
+}

test/src/unit-concepts.cpp

@@ -0,0 +1,169 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("concepts")
+{
+    SECTION("container requirements for json")
+    {
+        // X: container class: json
+        // T: type of objects: json
+        // a, b: values of type X: json
+
+        // TABLE 96 - Container Requirements
+
+        // X::value_type must return T
+        CHECK((std::is_same<json::value_type, json>::value));
+
+        // X::reference must return lvalue of T
+        CHECK((std::is_same<json::reference, json&>::value));
+
+        // X::const_reference must return const lvalue of T
+        CHECK((std::is_same<json::const_reference, const json&>::value));
+
+        // X::iterator must return iterator whose value_type is T
+        CHECK((std::is_same<json::iterator::value_type, json>::value));
+        // X::iterator must meet the forward iterator requirements
+        CHECK((std::is_base_of<std::forward_iterator_tag, typename std::iterator_traits<json::iterator>::iterator_category>::value));
+        // X::iterator must be convertible to X::const_iterator
+        CHECK((std::is_convertible<json::iterator, json::const_iterator>::value));
+
+        // X::const_iterator must return iterator whose value_type is T
+        CHECK((std::is_same<json::const_iterator::value_type, json>::value));
+        // X::const_iterator must meet the forward iterator requirements
+        CHECK((std::is_base_of<std::forward_iterator_tag, typename std::iterator_traits<json::const_iterator>::iterator_category>::value));
+
+        // X::difference_type must return a signed integer
+        CHECK((std::is_signed<json::difference_type>::value));
+        // X::difference_type must be identical to X::iterator::difference_type
+        CHECK((std::is_same<json::difference_type, json::iterator::difference_type>::value));
+        // X::difference_type must be identical to X::const_iterator::difference_type
+        CHECK((std::is_same<json::difference_type, json::const_iterator::difference_type>::value));
+
+        // X::size_type must return an unsigned integer
+        CHECK((std::is_unsigned<json::size_type>::value));
+        // X::size_type can represent any non-negative value of X::difference_type
+        CHECK(std::numeric_limits<json::difference_type>::max() <=
+              std::numeric_limits<json::size_type>::max());
+
+        // the expression "X u" has the post-condition "u.empty()"
+        {
+            json u;
+            CHECK(u.empty());
+        }
+
+        // the expression "X()" has the post-condition "X().empty()"
+        CHECK(json().empty());
+    }
+
+    SECTION("class json")
+    {
+        SECTION("DefaultConstructible")
+        {
+            CHECK(std::is_nothrow_default_constructible<json>::value);
+        }
+
+        SECTION("MoveConstructible")
+        {
+            CHECK(std::is_nothrow_move_constructible<json>::value);
+        }
+
+        SECTION("CopyConstructible")
+        {
+            CHECK(std::is_copy_constructible<json>::value);
+        }
+
+        SECTION("MoveAssignable")
+        {
+            CHECK(std::is_nothrow_move_assignable<json>::value);
+        }
+
+        SECTION("CopyAssignable")
+        {
+            CHECK(std::is_copy_assignable<json>::value);
+        }
+
+        SECTION("Destructible")
+        {
+            CHECK(std::is_nothrow_destructible<json>::value);
+        }
+
+        SECTION("StandardLayoutType")
+        {
+            CHECK(std::is_standard_layout<json>::value);
+        }
+    }
+
+    SECTION("class iterator")
+    {
+        SECTION("CopyConstructible")
+        {
+            CHECK(std::is_nothrow_copy_constructible<json::iterator>::value);
+            CHECK(std::is_nothrow_copy_constructible<json::const_iterator>::value);
+        }
+
+        SECTION("CopyAssignable")
+        {
+            // STL iterators used by json::iterator don't pass this test in Debug mode
+#if !defined(_MSC_VER) || (_ITERATOR_DEBUG_LEVEL == 0)
+            CHECK(std::is_nothrow_copy_assignable<json::iterator>::value);
+            CHECK(std::is_nothrow_copy_assignable<json::const_iterator>::value);
+#endif
+        }
+
+        SECTION("Destructible")
+        {
+            CHECK(std::is_nothrow_destructible<json::iterator>::value);
+            CHECK(std::is_nothrow_destructible<json::const_iterator>::value);
+        }
+
+        SECTION("Swappable")
+        {
+            {
+                json j {1, 2, 3};
+                json::iterator it1 = j.begin();
+                json::iterator it2 = j.end();
+                std::swap(it1, it2);
+                CHECK(it1 == j.end());
+                CHECK(it2 == j.begin());
+            }
+            {
+                json j {1, 2, 3};
+                json::const_iterator it1 = j.cbegin();
+                json::const_iterator it2 = j.cend();
+                std::swap(it1, it2);
+                CHECK(it1 == j.end());
+                CHECK(it2 == j.begin());
+            }
+        }
+    }
+}

test/src/unit-constructor2.cpp

@@ -0,0 +1,191 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("other constructors and destructor")
+{
+    SECTION("copy constructor")
+    {
+        SECTION("object")
+        {
+            json j {{"foo", 1}, {"bar", false}};
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("array")
+        {
+            json j {"foo", 1, 42.23, false};
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("null")
+        {
+            json j(nullptr);
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("boolean")
+        {
+            json j(true);
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("string")
+        {
+            json j("Hello world");
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("number (integer)")
+        {
+            json j(42);
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j(42u);
+            json k(j);
+            CHECK(j == k);
+        }
+
+        SECTION("number (floating-point)")
+        {
+            json j(42.23);
+            json k(j);
+            CHECK(j == k);
+        }
+    }
+
+    SECTION("move constructor")
+    {
+        json j {{"foo", "bar"}, {"baz", {1, 2, 3, 4}}, {"a", 42u}, {"b", 42.23}, {"c", nullptr}};
+        CHECK(j.type() == json::value_t::object);
+        json k(std::move(j));
+        CHECK(k.type() == json::value_t::object);
+        CHECK(j.type() == json::value_t::null);
+    }
+
+    SECTION("copy assignment")
+    {
+        SECTION("object")
+        {
+            json j {{"foo", 1}, {"bar", false}};
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("array")
+        {
+            json j {"foo", 1, 42.23, false};
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("null")
+        {
+            json j(nullptr);
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("boolean")
+        {
+            json j(true);
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("string")
+        {
+            json j("Hello world");
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("number (integer)")
+        {
+            json j(42);
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j(42u);
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+
+        SECTION("number (floating-point)")
+        {
+            json j(42.23);
+            json k;
+            k = j;
+            CHECK(j == k);
+        }
+    }
+
+    SECTION("destructor")
+    {
+        SECTION("object")
+        {
+            auto j = new json {{"foo", 1}, {"bar", false}};
+            delete j;
+        }
+
+        SECTION("array")
+        {
+            auto j = new json {"foo", 1, 1u, false, 23.42};
+            delete j;
+        }
+
+        SECTION("string")
+        {
+            auto j = new json("Hello world");
+            delete j;
+        }
+    }
+}

test/src/unit-convenience.cpp

@@ -0,0 +1,92 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("convenience functions")
+{
+    SECTION("type name as string")
+    {
+        CHECK(json(json::value_t::null).type_name() == "null");
+        CHECK(json(json::value_t::object).type_name() == "object");
+        CHECK(json(json::value_t::array).type_name() == "array");
+        CHECK(json(json::value_t::number_integer).type_name() == "number");
+        CHECK(json(json::value_t::number_unsigned).type_name() == "number");
+        CHECK(json(json::value_t::number_float).type_name() == "number");
+        CHECK(json(json::value_t::boolean).type_name() == "boolean");
+        CHECK(json(json::value_t::string).type_name() == "string");
+        CHECK(json(json::value_t::discarded).type_name() == "discarded");
+    }
+
+    SECTION("string escape")
+    {
+        CHECK(json::escape_string("\"") == "\\\"");
+        CHECK(json::escape_string("\\") == "\\\\");
+        CHECK(json::escape_string("\b") == "\\b");
+        CHECK(json::escape_string("\f") == "\\f");
+        CHECK(json::escape_string("\n") == "\\n");
+        CHECK(json::escape_string("\r") == "\\r");
+        CHECK(json::escape_string("\t") == "\\t");
+
+        CHECK(json::escape_string("\x01") == "\\u0001");
+        CHECK(json::escape_string("\x02") == "\\u0002");
+        CHECK(json::escape_string("\x03") == "\\u0003");
+        CHECK(json::escape_string("\x04") == "\\u0004");
+        CHECK(json::escape_string("\x05") == "\\u0005");
+        CHECK(json::escape_string("\x06") == "\\u0006");
+        CHECK(json::escape_string("\x07") == "\\u0007");
+        CHECK(json::escape_string("\x08") == "\\b");
+        CHECK(json::escape_string("\x09") == "\\t");
+        CHECK(json::escape_string("\x0a") == "\\n");
+        CHECK(json::escape_string("\x0b") == "\\u000b");
+        CHECK(json::escape_string("\x0c") == "\\f");
+        CHECK(json::escape_string("\x0d") == "\\r");
+        CHECK(json::escape_string("\x0e") == "\\u000e");
+        CHECK(json::escape_string("\x0f") == "\\u000f");
+        CHECK(json::escape_string("\x10") == "\\u0010");
+        CHECK(json::escape_string("\x11") == "\\u0011");
+        CHECK(json::escape_string("\x12") == "\\u0012");
+        CHECK(json::escape_string("\x13") == "\\u0013");
+        CHECK(json::escape_string("\x14") == "\\u0014");
+        CHECK(json::escape_string("\x15") == "\\u0015");
+        CHECK(json::escape_string("\x16") == "\\u0016");
+        CHECK(json::escape_string("\x17") == "\\u0017");
+        CHECK(json::escape_string("\x18") == "\\u0018");
+        CHECK(json::escape_string("\x19") == "\\u0019");
+        CHECK(json::escape_string("\x1a") == "\\u001a");
+        CHECK(json::escape_string("\x1b") == "\\u001b");
+        CHECK(json::escape_string("\x1c") == "\\u001c");
+        CHECK(json::escape_string("\x1d") == "\\u001d");
+        CHECK(json::escape_string("\x1e") == "\\u001e");
+        CHECK(json::escape_string("\x1f") == "\\u001f");
+    }
+}

test/src/unit-deserialization.cpp

@@ -0,0 +1,73 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("deserialization")
+{
+    SECTION("stream")
+    {
+        std::stringstream ss;
+        ss << "[\"foo\",1,2,3,false,{\"one\":1}]";
+        json j = json::parse(ss);
+        CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
+    }
+
+    SECTION("string")
+    {
+        auto s = "[\"foo\",1,2,3,false,{\"one\":1}]";
+        json j = json::parse(s);
+        CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
+    }
+
+    SECTION("operator<<")
+    {
+        std::stringstream ss;
+        ss << "[\"foo\",1,2,3,false,{\"one\":1}]";
+        json j;
+        j << ss;
+        CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
+    }
+
+    SECTION("operator>>")
+    {
+        std::stringstream ss;
+        ss << "[\"foo\",1,2,3,false,{\"one\":1}]";
+        json j;
+        ss >> j;
+        CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
+    }
+
+    SECTION("user-defined string literal")
+    {
+        CHECK("[\"foo\",1,2,3,false,{\"one\":1}]"_json == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
+    }
+}

test/src/unit-element_access1.cpp

@@ -0,0 +1,947 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("element access 1")
+{
+    SECTION("array")
+    {
+        json j = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+        const json j_const = j;
+
+        SECTION("access specified element with bounds checking")
+        {
+            SECTION("access within bounds")
+            {
+                CHECK(j.at(0) == json(1));
+                CHECK(j.at(1) == json(1u));
+                CHECK(j.at(2) == json(true));
+                CHECK(j.at(3) == json(nullptr));
+                CHECK(j.at(4) == json("string"));
+                CHECK(j.at(5) == json(42.23));
+                CHECK(j.at(6) == json(json::object()));
+                CHECK(j.at(7) == json({1, 2, 3}));
+
+                CHECK(j_const.at(0) == json(1));
+                CHECK(j_const.at(1) == json(1u));
+                CHECK(j_const.at(2) == json(true));
+                CHECK(j_const.at(3) == json(nullptr));
+                CHECK(j_const.at(4) == json("string"));
+                CHECK(j_const.at(5) == json(42.23));
+                CHECK(j_const.at(6) == json(json::object()));
+                CHECK(j_const.at(7) == json({1, 2, 3}));
+            }
+
+            SECTION("access outside bounds")
+            {
+                CHECK_THROWS_AS(j.at(8), std::out_of_range);
+                CHECK_THROWS_AS(j_const.at(8), std::out_of_range);
+
+                CHECK_THROWS_WITH(j.at(8), "array index 8 is out of range");
+                CHECK_THROWS_WITH(j_const.at(8), "array index 8 is out of range");
+            }
+
+            SECTION("access on non-array type")
+            {
+                SECTION("null")
+                {
+                    json j_nonarray(json::value_t::null);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with null");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with null");
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonarray(json::value_t::boolean);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with boolean");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonarray(json::value_t::string);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with string");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with string");
+                }
+
+                SECTION("object")
+                {
+                    json j_nonarray(json::value_t::object);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with object");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with object");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonarray(json::value_t::number_integer);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with number");
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonarray(json::value_t::number_unsigned);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonarray(json::value_t::number_float);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray.at(0), std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const.at(0), std::domain_error);
+
+                    CHECK_THROWS_WITH(j_nonarray.at(0), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonarray_const.at(0), "cannot use at() with number");
+                }
+            }
+        }
+
+        SECTION("front and back")
+        {
+            CHECK(j.front() == json(1));
+            CHECK(j_const.front() == json(1));
+            CHECK(j.back() == json({1, 2, 3}));
+            CHECK(j_const.back() == json({1, 2, 3}));
+        }
+
+        SECTION("access specified element")
+        {
+            SECTION("access within bounds")
+            {
+                CHECK(j[0] == json(1));
+                CHECK(j[1] == json(1u));
+                CHECK(j[2] == json(true));
+                CHECK(j[3] == json(nullptr));
+                CHECK(j[4] == json("string"));
+                CHECK(j[5] == json(42.23));
+                CHECK(j[6] == json(json::object()));
+                CHECK(j[7] == json({1, 2, 3}));
+
+                CHECK(j_const[0] == json(1));
+                CHECK(j_const[1] == json(1u));
+                CHECK(j_const[2] == json(true));
+                CHECK(j_const[3] == json(nullptr));
+                CHECK(j_const[4] == json("string"));
+                CHECK(j_const[5] == json(42.23));
+                CHECK(j_const[6] == json(json::object()));
+                CHECK(j_const[7] == json({1, 2, 3}));
+            }
+
+            SECTION("access on non-array type")
+            {
+                SECTION("null")
+                {
+                    SECTION("standard tests")
+                    {
+                        json j_nonarray(json::value_t::null);
+                        const json j_nonarray_const(j_nonarray);
+                        CHECK_NOTHROW(j_nonarray[0]);
+                        CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                        CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with null");
+                    }
+
+                    SECTION("implicit transformation to properly filled array")
+                    {
+                        json j_nonarray;
+                        j_nonarray[3] = 42;
+                        CHECK(j_nonarray == json({nullptr, nullptr, nullptr, 42}));
+                    }
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonarray(json::value_t::boolean);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with boolean");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonarray(json::value_t::string);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with string");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with string");
+                }
+
+                SECTION("object")
+                {
+                    json j_nonarray(json::value_t::object);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with object");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with object");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonarray(json::value_t::number_integer);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with number");
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonarray(json::value_t::number_unsigned);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonarray(json::value_t::number_float);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK_THROWS_AS(j_nonarray[0], std::domain_error);
+                    CHECK_THROWS_AS(j_nonarray_const[0], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonarray[0], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonarray_const[0], "cannot use operator[] with number");
+                }
+            }
+        }
+
+        SECTION("remove specified element")
+        {
+            SECTION("remove element by index")
+            {
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(0);
+                    CHECK(jarray == json({1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(1);
+                    CHECK(jarray == json({1, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(2);
+                    CHECK(jarray == json({1, 1u, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(3);
+                    CHECK(jarray == json({1, 1u, true, "string", 42.23, json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(4);
+                    CHECK(jarray == json({1, 1u, true, nullptr, 42.23, json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(5);
+                    CHECK(jarray == json({1, 1u, true, nullptr, "string", json::object(), {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(6);
+                    CHECK(jarray == json({1, 1u, true, nullptr, "string", 42.23, {1, 2, 3}}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    jarray.erase(7);
+                    CHECK(jarray == json({1, 1u, true, nullptr, "string", 42.23, json::object()}));
+                }
+                {
+                    json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                    CHECK_THROWS_AS(jarray.erase(8), std::out_of_range);
+                    CHECK_THROWS_WITH(jarray.erase(8), "array index 8 is out of range");
+                }
+            }
+
+            SECTION("remove element by iterator")
+            {
+                SECTION("erase(begin())")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::iterator it2 = jarray.erase(jarray.begin());
+                        CHECK(jarray == json({1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(1u));
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::const_iterator it2 = jarray.erase(jarray.cbegin());
+                        CHECK(jarray == json({1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(1u));
+                    }
+                }
+
+                SECTION("erase(begin(), end())")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::iterator it2 = jarray.erase(jarray.begin(), jarray.end());
+                        CHECK(jarray == json::array());
+                        CHECK(it2 == jarray.end());
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::const_iterator it2 = jarray.erase(jarray.cbegin(), jarray.cend());
+                        CHECK(jarray == json::array());
+                        CHECK(it2 == jarray.cend());
+                    }
+                }
+
+                SECTION("erase(begin(), begin())")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::iterator it2 = jarray.erase(jarray.begin(), jarray.begin());
+                        CHECK(jarray == json({1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(1));
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::const_iterator it2 = jarray.erase(jarray.cbegin(), jarray.cbegin());
+                        CHECK(jarray == json({1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(1));
+                    }
+                }
+
+                SECTION("erase at offset")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::iterator it = jarray.begin() + 4;
+                        json::iterator it2 = jarray.erase(it);
+                        CHECK(jarray == json({1, 1u, true, nullptr, 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(42.23));
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::const_iterator it = jarray.cbegin() + 4;
+                        json::const_iterator it2 = jarray.erase(it);
+                        CHECK(jarray == json({1, 1u, true, nullptr, 42.23, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json(42.23));
+                    }
+                }
+
+                SECTION("erase subrange")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::iterator it2 = jarray.erase(jarray.begin() + 3, jarray.begin() + 6);
+                        CHECK(jarray == json({1, 1u, true, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json::object());
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json::const_iterator it2 = jarray.erase(jarray.cbegin() + 3, jarray.cbegin() + 6);
+                        CHECK(jarray == json({1, 1u, true, json::object(), {1, 2, 3}}));
+                        CHECK(*it2 == json::object());
+                    }
+                }
+
+                SECTION("different arrays")
+                {
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json jarray2 = {"foo", "bar"};
+                        CHECK_THROWS_AS(jarray.erase(jarray2.begin()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray.begin(), jarray2.end()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray2.begin(), jarray.end()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray2.begin(), jarray2.end()), std::domain_error);
+
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.begin()), "iterator does not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray.begin(), jarray2.end()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.begin(), jarray.end()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.begin(), jarray2.end()),
+                                          "iterators do not fit current value");
+                    }
+                    {
+                        json jarray = {1, 1u, true, nullptr, "string", 42.23, json::object(), {1, 2, 3}};
+                        json jarray2 = {"foo", "bar"};
+                        CHECK_THROWS_AS(jarray.erase(jarray2.cbegin()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray.cbegin(), jarray2.cend()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray2.cbegin(), jarray.cend()), std::domain_error);
+                        CHECK_THROWS_AS(jarray.erase(jarray2.cbegin(), jarray2.cend()), std::domain_error);
+
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.cbegin()), "iterator does not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray.cbegin(), jarray2.cend()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.cbegin(), jarray.cend()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jarray.erase(jarray2.cbegin(), jarray2.cend()),
+                                          "iterators do not fit current value");
+                    }
+                }
+            }
+
+            SECTION("remove element by index in non-array type")
+            {
+                SECTION("null")
+                {
+                    json j_nonobject(json::value_t::null);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with null");
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonobject(json::value_t::boolean);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonobject(json::value_t::string);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with string");
+                }
+
+                SECTION("object")
+                {
+                    json j_nonobject(json::value_t::object);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with object");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonobject(json::value_t::number_integer);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with number");
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonobject(json::value_t::number_unsigned);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonobject(json::value_t::number_float);
+                    CHECK_THROWS_AS(j_nonobject.erase(0), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase(0), "cannot use erase() with number");
+                }
+            }
+        }
+    }
+
+    SECTION("other values")
+    {
+        SECTION("front and back")
+        {
+            SECTION("null")
+            {
+                {
+                    json j;
+                    CHECK_THROWS_AS(j.front(), std::out_of_range);
+                    CHECK_THROWS_AS(j.back(), std::out_of_range);
+                    CHECK_THROWS_WITH(j.front(), "cannot get value");
+                    CHECK_THROWS_WITH(j.back(), "cannot get value");
+                }
+                {
+                    const json j{};
+                    CHECK_THROWS_AS(j.front(), std::out_of_range);
+                    CHECK_THROWS_AS(j.back(), std::out_of_range);
+                    CHECK_THROWS_WITH(j.front(), "cannot get value");
+                    CHECK_THROWS_WITH(j.back(), "cannot get value");
+                }
+            }
+
+            SECTION("string")
+            {
+                {
+                    json j = "foo";
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+                {
+                    const json j = "bar";
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+            }
+
+            SECTION("number (boolean)")
+            {
+                {
+                    json j = false;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+                {
+                    const json j = true;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+            }
+
+            SECTION("number (integer)")
+            {
+                {
+                    json j = 17;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+                {
+                    const json j = 17;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+            }
+
+            SECTION("number (unsigned)")
+            {
+                {
+                    json j = 17u;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+                {
+                    const json j = 17u;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+            }
+
+            SECTION("number (floating point)")
+            {
+                {
+                    json j = 23.42;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+                {
+                    const json j = 23.42;
+                    CHECK(j.front() == j);
+                    CHECK(j.back() == j);
+                }
+            }
+        }
+
+        SECTION("erase with one valid iterator")
+        {
+            SECTION("null")
+            {
+                {
+                    json j;
+                    CHECK_THROWS_AS(j.erase(j.begin()), std::domain_error);
+                    CHECK_THROWS_WITH(j.erase(j.begin()), "cannot use erase() with null");
+                }
+                {
+                    json j;
+                    CHECK_THROWS_AS(j.erase(j.cbegin()), std::domain_error);
+                    CHECK_THROWS_WITH(j.erase(j.begin()), "cannot use erase() with null");
+                }
+            }
+
+            SECTION("string")
+            {
+                {
+                    json j = "foo";
+                    json::iterator it = j.erase(j.begin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = "bar";
+                    json::const_iterator it = j.erase(j.cbegin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (boolean)")
+            {
+                {
+                    json j = false;
+                    json::iterator it = j.erase(j.begin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = true;
+                    json::const_iterator it = j.erase(j.cbegin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (integer)")
+            {
+                {
+                    json j = 17;
+                    json::iterator it = j.erase(j.begin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 17;
+                    json::const_iterator it = j.erase(j.cbegin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (unsigned)")
+            {
+                {
+                    json j = 17u;
+                    json::iterator it = j.erase(j.begin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 17u;
+                    json::const_iterator it = j.erase(j.cbegin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (floating point)")
+            {
+                {
+                    json j = 23.42;
+                    json::iterator it = j.erase(j.begin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 23.42;
+                    json::const_iterator it = j.erase(j.cbegin());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+        }
+
+        SECTION("erase with one invalid iterator")
+        {
+            SECTION("string")
+            {
+                {
+                    json j = "foo";
+                    CHECK_THROWS_AS(j.erase(j.end()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end()), "iterator out of range");
+                }
+                {
+                    json j = "bar";
+                    CHECK_THROWS_AS(j.erase(j.cend()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend()), "iterator out of range");
+                }
+            }
+
+            SECTION("number (boolean)")
+            {
+                {
+                    json j = false;
+                    CHECK_THROWS_AS(j.erase(j.end()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end()), "iterator out of range");
+                }
+                {
+                    json j = true;
+                    CHECK_THROWS_AS(j.erase(j.cend()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend()), "iterator out of range");
+                }
+            }
+
+            SECTION("number (integer)")
+            {
+                {
+                    json j = 17;
+                    CHECK_THROWS_AS(j.erase(j.end()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end()), "iterator out of range");
+                }
+                {
+                    json j = 17;
+                    CHECK_THROWS_AS(j.erase(j.cend()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend()), "iterator out of range");
+                }
+            }
+
+            SECTION("number (unsigned)")
+            {
+                {
+                    json j = 17u;
+                    CHECK_THROWS_AS(j.erase(j.end()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end()), "iterator out of range");
+                }
+                {
+                    json j = 17u;
+                    CHECK_THROWS_AS(j.erase(j.cend()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend()), "iterator out of range");
+                }
+            }
+
+            SECTION("number (floating point)")
+            {
+                {
+                    json j = 23.42;
+                    CHECK_THROWS_AS(j.erase(j.end()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end()), "iterator out of range");
+                }
+                {
+                    json j = 23.42;
+                    CHECK_THROWS_AS(j.erase(j.cend()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend()), "iterator out of range");
+                }
+            }
+        }
+
+        SECTION("erase with two valid iterators")
+        {
+            SECTION("null")
+            {
+                {
+                    json j;
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.end()), std::domain_error);
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.end()), "cannot use erase() with null");
+                }
+                {
+                    json j;
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cend()), std::domain_error);
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cend()), "cannot use erase() with null");
+                }
+            }
+
+            SECTION("string")
+            {
+                {
+                    json j = "foo";
+                    json::iterator it = j.erase(j.begin(), j.end());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = "bar";
+                    json::const_iterator it = j.erase(j.cbegin(), j.cend());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (boolean)")
+            {
+                {
+                    json j = false;
+                    json::iterator it = j.erase(j.begin(), j.end());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = true;
+                    json::const_iterator it = j.erase(j.cbegin(), j.cend());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (integer)")
+            {
+                {
+                    json j = 17;
+                    json::iterator it = j.erase(j.begin(), j.end());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 17;
+                    json::const_iterator it = j.erase(j.cbegin(), j.cend());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (unsigned)")
+            {
+                {
+                    json j = 17u;
+                    json::iterator it = j.erase(j.begin(), j.end());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 17u;
+                    json::const_iterator it = j.erase(j.cbegin(), j.cend());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+
+            SECTION("number (floating point)")
+            {
+                {
+                    json j = 23.42;
+                    json::iterator it = j.erase(j.begin(), j.end());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+                {
+                    json j = 23.42;
+                    json::const_iterator it = j.erase(j.cbegin(), j.cend());
+                    CHECK(j.type() == json::value_t::null);
+                    CHECK(it == j.end());
+                }
+            }
+        }
+
+        SECTION("erase with two invalid iterators")
+        {
+            SECTION("string")
+            {
+                {
+                    json j = "foo";
+                    CHECK_THROWS_AS(j.erase(j.end(), j.end()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.begin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end(), j.end()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.begin()), "iterators out of range");
+                }
+                {
+                    json j = "bar";
+                    CHECK_THROWS_AS(j.erase(j.cend(), j.cend()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cbegin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend(), j.cend()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cbegin()), "iterators out of range");
+                }
+            }
+
+            SECTION("number (boolean)")
+            {
+                {
+                    json j = false;
+                    CHECK_THROWS_AS(j.erase(j.end(), j.end()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.begin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end(), j.end()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.begin()), "iterators out of range");
+                }
+                {
+                    json j = true;
+                    CHECK_THROWS_AS(j.erase(j.cend(), j.cend()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cbegin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend(), j.cend()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cbegin()), "iterators out of range");
+                }
+            }
+
+            SECTION("number (integer)")
+            {
+                {
+                    json j = 17;
+                    CHECK_THROWS_AS(j.erase(j.end(), j.end()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.begin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end(), j.end()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.begin()), "iterators out of range");
+                }
+                {
+                    json j = 17;
+                    CHECK_THROWS_AS(j.erase(j.cend(), j.cend()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cbegin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend(), j.cend()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cbegin()), "iterators out of range");
+                }
+            }
+
+            SECTION("number (unsigned)")
+            {
+                {
+                    json j = 17u;
+                    CHECK_THROWS_AS(j.erase(j.end(), j.end()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.begin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end(), j.end()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.begin()), "iterators out of range");
+                }
+                {
+                    json j = 17u;
+                    CHECK_THROWS_AS(j.erase(j.cend(), j.cend()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cbegin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend(), j.cend()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cbegin()), "iterators out of range");
+                }
+            }
+
+            SECTION("number (floating point)")
+            {
+                {
+                    json j = 23.42;
+                    CHECK_THROWS_AS(j.erase(j.end(), j.end()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.begin(), j.begin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.end(), j.end()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.begin(), j.begin()), "iterators out of range");
+                }
+                {
+                    json j = 23.42;
+                    CHECK_THROWS_AS(j.erase(j.cend(), j.cend()), std::out_of_range);
+                    CHECK_THROWS_AS(j.erase(j.cbegin(), j.cbegin()), std::out_of_range);
+                    CHECK_THROWS_WITH(j.erase(j.cend(), j.cend()), "iterators out of range");
+                    CHECK_THROWS_WITH(j.erase(j.cbegin(), j.cbegin()), "iterators out of range");
+                }
+            }
+        }
+    }
+}

test/src/unit-element_access2.cpp

@@ -0,0 +1,959 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("element access 2")
+{
+    SECTION("object")
+    {
+        json j = {{"integer", 1}, {"unsigned", 1u}, {"floating", 42.23}, {"null", nullptr}, {"string", "hello world"}, {"boolean", true}, {"object", json::object()}, {"array", {1, 2, 3}}};
+        const json j_const = j;
+
+        SECTION("access specified element with bounds checking")
+        {
+            SECTION("access within bounds")
+            {
+                CHECK(j.at("integer") == json(1));
+                CHECK(j.at("unsigned") == json(1u));
+                CHECK(j.at("boolean") == json(true));
+                CHECK(j.at("null") == json(nullptr));
+                CHECK(j.at("string") == json("hello world"));
+                CHECK(j.at("floating") == json(42.23));
+                CHECK(j.at("object") == json(json::object()));
+                CHECK(j.at("array") == json({1, 2, 3}));
+
+                CHECK(j_const.at("integer") == json(1));
+                CHECK(j_const.at("unsigned") == json(1u));
+                CHECK(j_const.at("boolean") == json(true));
+                CHECK(j_const.at("null") == json(nullptr));
+                CHECK(j_const.at("string") == json("hello world"));
+                CHECK(j_const.at("floating") == json(42.23));
+                CHECK(j_const.at("object") == json(json::object()));
+                CHECK(j_const.at("array") == json({1, 2, 3}));
+            }
+
+            SECTION("access outside bounds")
+            {
+                CHECK_THROWS_AS(j.at("foo"), std::out_of_range);
+                CHECK_THROWS_AS(j_const.at("foo"), std::out_of_range);
+                CHECK_THROWS_WITH(j.at("foo"), "key 'foo' not found");
+                CHECK_THROWS_WITH(j_const.at("foo"), "key 'foo' not found");
+            }
+
+            SECTION("access on non-object type")
+            {
+                SECTION("null")
+                {
+                    json j_nonobject(json::value_t::null);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with null");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with null");
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonobject(json::value_t::boolean);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with boolean");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonobject(json::value_t::string);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with string");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with string");
+                }
+
+                SECTION("array")
+                {
+                    json j_nonobject(json::value_t::array);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with array");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with array");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonobject(json::value_t::number_integer);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with number");
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonobject(json::value_t::number_unsigned);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonobject(json::value_t::number_float);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject.at("foo"), std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject_const.at("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.at("foo"), "cannot use at() with number");
+                    CHECK_THROWS_WITH(j_nonobject_const.at("foo"), "cannot use at() with number");
+                }
+            }
+        }
+
+        SECTION("access specified element with default value")
+        {
+            SECTION("given a key")
+            {
+                SECTION("access existing value")
+                {
+                    CHECK(j.value("integer", 2) == 1);
+                    CHECK(j.value("integer", 1.0) == Approx(1));
+                    CHECK(j.value("unsigned", 2) == 1u);
+                    CHECK(j.value("unsigned", 1.0) == Approx(1u));
+                    CHECK(j.value("null", json(1)) == json());
+                    CHECK(j.value("boolean", false) == true);
+                    CHECK(j.value("string", "bar") == "hello world");
+                    CHECK(j.value("string", std::string("bar")) == "hello world");
+                    CHECK(j.value("floating", 12.34) == Approx(42.23));
+                    CHECK(j.value("floating", 12) == 42);
+                    CHECK(j.value("object", json({{"foo", "bar"}})) == json(json::object()));
+                    CHECK(j.value("array", json({10, 100})) == json({1, 2, 3}));
+
+                    CHECK(j_const.value("integer", 2) == 1);
+                    CHECK(j_const.value("integer", 1.0) == Approx(1));
+                    CHECK(j_const.value("unsigned", 2) == 1u);
+                    CHECK(j_const.value("unsigned", 1.0) == Approx(1u));
+                    CHECK(j_const.value("boolean", false) == true);
+                    CHECK(j_const.value("string", "bar") == "hello world");
+                    CHECK(j_const.value("string", std::string("bar")) == "hello world");
+                    CHECK(j_const.value("floating", 12.34) == Approx(42.23));
+                    CHECK(j_const.value("floating", 12) == 42);
+                    CHECK(j_const.value("object", json({{"foo", "bar"}})) == json(json::object()));
+                    CHECK(j_const.value("array", json({10, 100})) == json({1, 2, 3}));
+                }
+
+                SECTION("access non-existing value")
+                {
+                    CHECK(j.value("_", 2) == 2);
+                    CHECK(j.value("_", 2u) == 2u);
+                    CHECK(j.value("_", false) == false);
+                    CHECK(j.value("_", "bar") == "bar");
+                    CHECK(j.value("_", 12.34) == Approx(12.34));
+                    CHECK(j.value("_", json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j.value("_", json({10, 100})) == json({10, 100}));
+
+                    CHECK(j_const.value("_", 2) == 2);
+                    CHECK(j_const.value("_", 2u) == 2u);
+                    CHECK(j_const.value("_", false) == false);
+                    CHECK(j_const.value("_", "bar") == "bar");
+                    CHECK(j_const.value("_", 12.34) == Approx(12.34));
+                    CHECK(j_const.value("_", json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j_const.value("_", json({10, 100})) == json({10, 100}));
+                }
+
+                SECTION("access on non-object type")
+                {
+                    SECTION("null")
+                    {
+                        json j_nonobject(json::value_t::null);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with null");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with null");
+                    }
+
+                    SECTION("boolean")
+                    {
+                        json j_nonobject(json::value_t::boolean);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with boolean");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with boolean");
+                    }
+
+                    SECTION("string")
+                    {
+                        json j_nonobject(json::value_t::string);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with string");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with string");
+                    }
+
+                    SECTION("array")
+                    {
+                        json j_nonobject(json::value_t::array);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with array");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with array");
+                    }
+
+                    SECTION("number (integer)")
+                    {
+                        json j_nonobject(json::value_t::number_integer);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with number");
+                    }
+
+                    SECTION("number (unsigned)")
+                    {
+                        json j_nonobject(json::value_t::number_unsigned);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with number");
+                    }
+
+                    SECTION("number (floating-point)")
+                    {
+                        json j_nonobject(json::value_t::number_float);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("foo", 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("foo", 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("foo", 1), "cannot use value() with number");
+                    }
+                }
+            }
+
+            SECTION("given a JSON pointer")
+            {
+                SECTION("access existing value")
+                {
+                    CHECK(j.value("/integer"_json_pointer, 2) == 1);
+                    CHECK(j.value("/integer"_json_pointer, 1.0) == Approx(1));
+                    CHECK(j.value("/unsigned"_json_pointer, 2) == 1u);
+                    CHECK(j.value("/unsigned"_json_pointer, 1.0) == Approx(1u));
+                    CHECK(j.value("/null"_json_pointer, json(1)) == json());
+                    CHECK(j.value("/boolean"_json_pointer, false) == true);
+                    CHECK(j.value("/string"_json_pointer, "bar") == "hello world");
+                    CHECK(j.value("/string"_json_pointer, std::string("bar")) == "hello world");
+                    CHECK(j.value("/floating"_json_pointer, 12.34) == Approx(42.23));
+                    CHECK(j.value("/floating"_json_pointer, 12) == 42);
+                    CHECK(j.value("/object"_json_pointer, json({{"foo", "bar"}})) == json(json::object()));
+                    CHECK(j.value("/array"_json_pointer, json({10, 100})) == json({1, 2, 3}));
+
+                    CHECK(j_const.value("/integer"_json_pointer, 2) == 1);
+                    CHECK(j_const.value("/integer"_json_pointer, 1.0) == Approx(1));
+                    CHECK(j_const.value("/unsigned"_json_pointer, 2) == 1u);
+                    CHECK(j_const.value("/unsigned"_json_pointer, 1.0) == Approx(1u));
+                    CHECK(j_const.value("/boolean"_json_pointer, false) == true);
+                    CHECK(j_const.value("/string"_json_pointer, "bar") == "hello world");
+                    CHECK(j_const.value("/string"_json_pointer, std::string("bar")) == "hello world");
+                    CHECK(j_const.value("/floating"_json_pointer, 12.34) == Approx(42.23));
+                    CHECK(j_const.value("/floating"_json_pointer, 12) == 42);
+                    CHECK(j_const.value("/object"_json_pointer, json({{"foo", "bar"}})) == json(json::object()));
+                    CHECK(j_const.value("/array"_json_pointer, json({10, 100})) == json({1, 2, 3}));
+                }
+
+                SECTION("access non-existing value")
+                {
+                    CHECK(j.value("/not/existing"_json_pointer, 2) == 2);
+                    CHECK(j.value("/not/existing"_json_pointer, 2u) == 2u);
+                    CHECK(j.value("/not/existing"_json_pointer, false) == false);
+                    CHECK(j.value("/not/existing"_json_pointer, "bar") == "bar");
+                    CHECK(j.value("/not/existing"_json_pointer, 12.34) == Approx(12.34));
+                    CHECK(j.value("/not/existing"_json_pointer, json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j.value("/not/existing"_json_pointer, json({10, 100})) == json({10, 100}));
+
+                    CHECK(j_const.value("/not/existing"_json_pointer, 2) == 2);
+                    CHECK(j_const.value("/not/existing"_json_pointer, 2u) == 2u);
+                    CHECK(j_const.value("/not/existing"_json_pointer, false) == false);
+                    CHECK(j_const.value("/not/existing"_json_pointer, "bar") == "bar");
+                    CHECK(j_const.value("/not/existing"_json_pointer, 12.34) == Approx(12.34));
+                    CHECK(j_const.value("/not/existing"_json_pointer, json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j_const.value("/not/existing"_json_pointer, json({10, 100})) == json({10, 100}));
+                }
+
+                SECTION("access on non-object type")
+                {
+                    SECTION("null")
+                    {
+                        json j_nonobject(json::value_t::null);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with null");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1), "cannot use value() with null");
+                    }
+
+                    SECTION("boolean")
+                    {
+                        json j_nonobject(json::value_t::boolean);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with boolean");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1),
+                                          "cannot use value() with boolean");
+                    }
+
+                    SECTION("string")
+                    {
+                        json j_nonobject(json::value_t::string);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with string");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1),
+                                          "cannot use value() with string");
+                    }
+
+                    SECTION("array")
+                    {
+                        json j_nonobject(json::value_t::array);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with array");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1), "cannot use value() with array");
+                    }
+
+                    SECTION("number (integer)")
+                    {
+                        json j_nonobject(json::value_t::number_integer);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1),
+                                          "cannot use value() with number");
+                    }
+
+                    SECTION("number (unsigned)")
+                    {
+                        json j_nonobject(json::value_t::number_unsigned);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1),
+                                          "cannot use value() with number");
+                    }
+
+                    SECTION("number (floating-point)")
+                    {
+                        json j_nonobject(json::value_t::number_float);
+                        const json j_nonobject_const(j_nonobject);
+                        CHECK_THROWS_AS(j_nonobject.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_AS(j_nonobject_const.value("/foo"_json_pointer, 1), std::domain_error);
+                        CHECK_THROWS_WITH(j_nonobject.value("/foo"_json_pointer, 1), "cannot use value() with number");
+                        CHECK_THROWS_WITH(j_nonobject_const.value("/foo"_json_pointer, 1),
+                                          "cannot use value() with number");
+                    }
+                }
+            }
+        }
+
+        SECTION("front and back")
+        {
+            // "array" is the smallest key
+            CHECK(j.front() == json({1, 2, 3}));
+            CHECK(j_const.front() == json({1, 2, 3}));
+            // "unsigned" is the largest key
+            CHECK(j.back() == json(1u));
+            CHECK(j_const.back() == json(1u));
+        }
+
+        SECTION("access specified element")
+        {
+            SECTION("access within bounds")
+            {
+                CHECK(j["integer"] == json(1));
+                CHECK(j[json::object_t::key_type("integer")] == j["integer"]);
+
+                CHECK(j["unsigned"] == json(1u));
+                CHECK(j[json::object_t::key_type("unsigned")] == j["unsigned"]);
+
+                CHECK(j["boolean"] == json(true));
+                CHECK(j[json::object_t::key_type("boolean")] == j["boolean"]);
+
+                CHECK(j["null"] == json(nullptr));
+                CHECK(j[json::object_t::key_type("null")] == j["null"]);
+
+                CHECK(j["string"] == json("hello world"));
+                CHECK(j[json::object_t::key_type("string")] == j["string"]);
+
+                CHECK(j["floating"] == json(42.23));
+                CHECK(j[json::object_t::key_type("floating")] == j["floating"]);
+
+                CHECK(j["object"] == json(json::object()));
+                CHECK(j[json::object_t::key_type("object")] == j["object"]);
+
+                CHECK(j["array"] == json({1, 2, 3}));
+                CHECK(j[json::object_t::key_type("array")] == j["array"]);
+
+                CHECK(j_const["integer"] == json(1));
+                CHECK(j_const[json::object_t::key_type("integer")] == j["integer"]);
+
+                CHECK(j_const["boolean"] == json(true));
+                CHECK(j_const[json::object_t::key_type("boolean")] == j["boolean"]);
+
+                CHECK(j_const["null"] == json(nullptr));
+                CHECK(j_const[json::object_t::key_type("null")] == j["null"]);
+
+                CHECK(j_const["string"] == json("hello world"));
+                CHECK(j_const[json::object_t::key_type("string")] == j["string"]);
+
+                CHECK(j_const["floating"] == json(42.23));
+                CHECK(j_const[json::object_t::key_type("floating")] == j["floating"]);
+
+                CHECK(j_const["object"] == json(json::object()));
+                CHECK(j_const[json::object_t::key_type("object")] == j["object"]);
+
+                CHECK(j_const["array"] == json({1, 2, 3}));
+                CHECK(j_const[json::object_t::key_type("array")] == j["array"]);
+            }
+
+            SECTION("access on non-object type")
+            {
+                SECTION("null")
+                {
+                    json j_nonobject(json::value_t::null);
+                    json j_nonobject2(json::value_t::null);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_NOTHROW(j_nonobject["foo"]);
+                    CHECK_NOTHROW(j_nonobject2[json::object_t::key_type("foo")]);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with null");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with null");
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonobject(json::value_t::boolean);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with boolean");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with boolean");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with boolean");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonobject(json::value_t::string);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with string");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with string");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with string");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with string");
+                }
+
+                SECTION("array")
+                {
+                    json j_nonobject(json::value_t::array);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with array");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")], "cannot use operator[] with array");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with array");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with array");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonobject(json::value_t::number_integer);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonobject(json::value_t::number_unsigned);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonobject(json::value_t::number_float);
+                    const json j_const_nonobject(j_nonobject);
+                    CHECK_THROWS_AS(j_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject["foo"], std::domain_error);
+                    CHECK_THROWS_AS(j_const_nonobject[json::object_t::key_type("foo")], std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject["foo"], "cannot use operator[] with number");
+                    CHECK_THROWS_WITH(j_const_nonobject[json::object_t::key_type("foo")],
+                                      "cannot use operator[] with number");
+                }
+            }
+        }
+
+        SECTION("remove specified element")
+        {
+            SECTION("remove element by key")
+            {
+                CHECK(j.find("integer") != j.end());
+                CHECK(j.erase("integer") == 1);
+                CHECK(j.find("integer") == j.end());
+                CHECK(j.erase("integer") == 0);
+
+                CHECK(j.find("unsigned") != j.end());
+                CHECK(j.erase("unsigned") == 1);
+                CHECK(j.find("unsigned") == j.end());
+                CHECK(j.erase("unsigned") == 0);
+
+                CHECK(j.find("boolean") != j.end());
+                CHECK(j.erase("boolean") == 1);
+                CHECK(j.find("boolean") == j.end());
+                CHECK(j.erase("boolean") == 0);
+
+                CHECK(j.find("null") != j.end());
+                CHECK(j.erase("null") == 1);
+                CHECK(j.find("null") == j.end());
+                CHECK(j.erase("null") == 0);
+
+                CHECK(j.find("string") != j.end());
+                CHECK(j.erase("string") == 1);
+                CHECK(j.find("string") == j.end());
+                CHECK(j.erase("string") == 0);
+
+                CHECK(j.find("floating") != j.end());
+                CHECK(j.erase("floating") == 1);
+                CHECK(j.find("floating") == j.end());
+                CHECK(j.erase("floating") == 0);
+
+                CHECK(j.find("object") != j.end());
+                CHECK(j.erase("object") == 1);
+                CHECK(j.find("object") == j.end());
+                CHECK(j.erase("object") == 0);
+
+                CHECK(j.find("array") != j.end());
+                CHECK(j.erase("array") == 1);
+                CHECK(j.find("array") == j.end());
+                CHECK(j.erase("array") == 0);
+            }
+
+            SECTION("remove element by iterator")
+            {
+                SECTION("erase(begin())")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::iterator it2 = jobject.erase(jobject.begin());
+                        CHECK(jobject == json({{"b", 1}, {"c", 17u}}));
+                        CHECK(*it2 == json(1));
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::const_iterator it2 = jobject.erase(jobject.cbegin());
+                        CHECK(jobject == json({{"b", 1}, {"c", 17u}}));
+                        CHECK(*it2 == json(1));
+                    }
+                }
+
+                SECTION("erase(begin(), end())")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::iterator it2 = jobject.erase(jobject.begin(), jobject.end());
+                        CHECK(jobject == json::object());
+                        CHECK(it2 == jobject.end());
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::const_iterator it2 = jobject.erase(jobject.cbegin(), jobject.cend());
+                        CHECK(jobject == json::object());
+                        CHECK(it2 == jobject.cend());
+                    }
+                }
+
+                SECTION("erase(begin(), begin())")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::iterator it2 = jobject.erase(jobject.begin(), jobject.begin());
+                        CHECK(jobject == json({{"a", "a"}, {"b", 1}, {"c", 17u}}));
+                        CHECK(*it2 == json("a"));
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::const_iterator it2 = jobject.erase(jobject.cbegin(), jobject.cbegin());
+                        CHECK(jobject == json({{"a", "a"}, {"b", 1}, {"c", 17u}}));
+                        CHECK(*it2 == json("a"));
+                    }
+                }
+
+                SECTION("erase at offset")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::iterator it = jobject.find("b");
+                        json::iterator it2 = jobject.erase(it);
+                        CHECK(jobject == json({{"a", "a"}, {"c", 17u}}));
+                        CHECK(*it2 == json(17));
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        json::const_iterator it = jobject.find("b");
+                        json::const_iterator it2 = jobject.erase(it);
+                        CHECK(jobject == json({{"a", "a"}, {"c", 17u}}));
+                        CHECK(*it2 == json(17));
+                    }
+                }
+
+                SECTION("erase subrange")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}, {"d", false}, {"e", true}};
+                        json::iterator it2 = jobject.erase(jobject.find("b"), jobject.find("e"));
+                        CHECK(jobject == json({{"a", "a"}, {"e", true}}));
+                        CHECK(*it2 == json(true));
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}, {"d", false}, {"e", true}};
+                        json::const_iterator it2 = jobject.erase(jobject.find("b"), jobject.find("e"));
+                        CHECK(jobject == json({{"a", "a"}, {"e", true}}));
+                        CHECK(*it2 == json(true));
+                    }
+                }
+
+                SECTION("different objects")
+                {
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}, {"d", false}, {"e", true}};
+                        json jobject2 = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        CHECK_THROWS_AS(jobject.erase(jobject2.begin()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject.begin(), jobject2.end()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject2.begin(), jobject.end()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject2.begin(), jobject2.end()), std::domain_error);
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.begin()), "iterator does not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject.begin(), jobject2.end()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.begin(), jobject.end()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.begin(), jobject2.end()),
+                                          "iterators do not fit current value");
+                    }
+                    {
+                        json jobject = {{"a", "a"}, {"b", 1}, {"c", 17u}, {"d", false}, {"e", true}};
+                        json jobject2 = {{"a", "a"}, {"b", 1}, {"c", 17u}};
+                        CHECK_THROWS_AS(jobject.erase(jobject2.cbegin()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject.cbegin(), jobject2.cend()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject2.cbegin(), jobject.cend()), std::domain_error);
+                        CHECK_THROWS_AS(jobject.erase(jobject2.cbegin(), jobject2.cend()), std::domain_error);
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.cbegin()), "iterator does not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject.cbegin(), jobject2.cend()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.cbegin(), jobject.cend()),
+                                          "iterators do not fit current value");
+                        CHECK_THROWS_WITH(jobject.erase(jobject2.cbegin(), jobject2.cend()),
+                                          "iterators do not fit current value");
+                    }
+                }
+            }
+
+            SECTION("remove element by key in non-object type")
+            {
+                SECTION("null")
+                {
+                    json j_nonobject(json::value_t::null);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with null");
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonobject(json::value_t::boolean);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with boolean");
+                }
+
+                SECTION("string")
+                {
+                    json j_nonobject(json::value_t::string);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with string");
+                }
+
+                SECTION("array")
+                {
+                    json j_nonobject(json::value_t::array);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with array");
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonobject(json::value_t::number_integer);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with number");
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonobject(json::value_t::number_float);
+                    CHECK_THROWS_AS(j_nonobject.erase("foo"), std::domain_error);
+                    CHECK_THROWS_WITH(j_nonobject.erase("foo"), "cannot use erase() with number");
+                }
+            }
+        }
+
+        SECTION("find an element in an object")
+        {
+            SECTION("existing element")
+            {
+                for (auto key :
+                        {"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
+                        })
+                {
+                    CHECK(j.find(key) != j.end());
+                    CHECK(*j.find(key) == j.at(key));
+                    CHECK(j_const.find(key) != j_const.end());
+                    CHECK(*j_const.find(key) == j_const.at(key));
+                }
+            }
+
+            SECTION("nonexisting element")
+            {
+                CHECK(j.find("foo") == j.end());
+                CHECK(j_const.find("foo") == j_const.end());
+            }
+
+            SECTION("all types")
+            {
+                SECTION("null")
+                {
+                    json j_nonarray(json::value_t::null);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("string")
+                {
+                    json j_nonarray(json::value_t::string);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("object")
+                {
+                    json j_nonarray(json::value_t::object);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("array")
+                {
+                    json j_nonarray(json::value_t::array);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonarray(json::value_t::boolean);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonarray(json::value_t::number_integer);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonarray(json::value_t::number_unsigned);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonarray(json::value_t::number_float);
+                    const json j_nonarray_const(j_nonarray);
+                    CHECK(j_nonarray.find("foo") == j_nonarray.end());
+                    CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+                }
+            }
+        }
+
+        SECTION("count keys in an object")
+        {
+            SECTION("existing element")
+            {
+                for (auto key :
+                        {"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
+                        })
+                {
+                    CHECK(j.count(key) == 1);
+                    CHECK(j_const.count(key) == 1);
+                }
+            }
+
+            SECTION("nonexisting element")
+            {
+                CHECK(j.count("foo") == 0);
+                CHECK(j_const.count("foo") == 0);
+            }
+
+            SECTION("all types")
+            {
+                SECTION("null")
+                {
+                    json j_nonobject(json::value_t::null);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("string")
+                {
+                    json j_nonobject(json::value_t::string);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("object")
+                {
+                    json j_nonobject(json::value_t::object);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("array")
+                {
+                    json j_nonobject(json::value_t::array);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("boolean")
+                {
+                    json j_nonobject(json::value_t::boolean);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("number (integer)")
+                {
+                    json j_nonobject(json::value_t::number_integer);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("number (unsigned)")
+                {
+                    json j_nonobject(json::value_t::number_unsigned);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+
+                SECTION("number (floating-point)")
+                {
+                    json j_nonobject(json::value_t::number_float);
+                    const json j_nonobject_const(j_nonobject);
+                    CHECK(j_nonobject.count("foo") == 0);
+                    CHECK(j_nonobject_const.count("foo") == 0);
+                }
+            }
+        }
+    }
+}

test/src/unit-inspection.cpp

@@ -0,0 +1,373 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("object inspection")
+{
+    SECTION("convenience type checker")
+    {
+        SECTION("object")
+        {
+            json j {{"foo", 1}, {"bar", false}};
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(not j.is_primitive());
+            CHECK(j.is_structured());
+        }
+
+        SECTION("array")
+        {
+            json j {"foo", 1, 1u, 42.23, false};
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(not j.is_primitive());
+            CHECK(j.is_structured());
+        }
+
+        SECTION("null")
+        {
+            json j(nullptr);
+            CHECK(j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("boolean")
+        {
+            json j(true);
+            CHECK(not j.is_null());
+            CHECK(j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("string")
+        {
+            json j("Hello world");
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("number (integer)")
+        {
+            json j(42);
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(j.is_number());
+            CHECK(j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j(42u);
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(j.is_number());
+            CHECK(j.is_number_integer());
+            CHECK(j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("number (floating-point)")
+        {
+            json j(42.23);
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(not j.is_discarded());
+            CHECK(j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+
+        SECTION("discarded")
+        {
+            json j(json::value_t::discarded);
+            CHECK(not j.is_null());
+            CHECK(not j.is_boolean());
+            CHECK(not j.is_number());
+            CHECK(not j.is_number_integer());
+            CHECK(not j.is_number_unsigned());
+            CHECK(not j.is_number_float());
+            CHECK(not j.is_object());
+            CHECK(not j.is_array());
+            CHECK(not j.is_string());
+            CHECK(j.is_discarded());
+            CHECK(not j.is_primitive());
+            CHECK(not j.is_structured());
+        }
+    }
+
+    SECTION("serialization")
+    {
+        json j {{"object", json::object()}, {"array", {1, 2, 3, 4}}, {"number", 42}, {"boolean", false}, {"null", nullptr}, {"string", "Hello world"} };
+
+        SECTION("no indent / indent=-1")
+        {
+            CHECK(j.dump() ==
+                  "{\"array\":[1,2,3,4],\"boolean\":false,\"null\":null,\"number\":42,\"object\":{},\"string\":\"Hello world\"}");
+
+            CHECK(j.dump() == j.dump(-1));
+        }
+
+        SECTION("indent=0")
+        {
+            CHECK(j.dump(0) ==
+                  "{\n\"array\": [\n1,\n2,\n3,\n4\n],\n\"boolean\": false,\n\"null\": null,\n\"number\": 42,\n\"object\": {},\n\"string\": \"Hello world\"\n}");
+        }
+
+        SECTION("indent=4")
+        {
+            CHECK(j.dump(4) ==
+                  "{\n    \"array\": [\n        1,\n        2,\n        3,\n        4\n    ],\n    \"boolean\": false,\n    \"null\": null,\n    \"number\": 42,\n    \"object\": {},\n    \"string\": \"Hello world\"\n}");
+        }
+
+        SECTION("dump and floating-point numbers")
+        {
+            auto s = json(42.23).dump();
+            CHECK(s.find("42.23") != std::string::npos);
+        }
+
+        SECTION("dump and small floating-point numbers")
+        {
+            auto s = json(1.23456e-78).dump();
+            CHECK(s.find("1.23456e-78") != std::string::npos);
+        }
+
+        SECTION("dump and non-ASCII characters")
+        {
+            CHECK(json("ä").dump() == "\"ä\"");
+            CHECK(json("Ö").dump() == "\"Ö\"");
+            CHECK(json("❤️").dump() == "\"❤️\"");
+        }
+
+        SECTION("serialization of discarded element")
+        {
+            json j_discarded(json::value_t::discarded);
+            CHECK(j_discarded.dump() == "<discarded>");
+        }
+
+        SECTION("check that precision is reset after serialization")
+        {
+            // create stringstream and set precision
+            std::stringstream ss;
+            ss.precision(3);
+            ss << 3.141592653589793 << std::fixed;
+            CHECK(ss.str() == "3.14");
+
+            // reset stringstream
+            ss.str(std::string());
+
+            // use stringstream for JSON serialization
+            json j_number = 3.141592653589793;
+            ss << j_number;
+
+            // check that precision has been overridden during serialization
+            CHECK(ss.str() == "3.141592653589793");
+
+            // check that precision has been restored
+            CHECK(ss.precision() == 3);
+        }
+    }
+
+    SECTION("return the type of the object (explicit)")
+    {
+        SECTION("null")
+        {
+            json j = nullptr;
+            CHECK(j.type() == json::value_t::null);
+        }
+
+        SECTION("object")
+        {
+            json j = {{"foo", "bar"}};
+            CHECK(j.type() == json::value_t::object);
+        }
+
+        SECTION("array")
+        {
+            json j = {1, 2, 3, 4};
+            CHECK(j.type() == json::value_t::array);
+        }
+
+        SECTION("boolean")
+        {
+            json j = true;
+            CHECK(j.type() == json::value_t::boolean);
+        }
+
+        SECTION("string")
+        {
+            json j = "Hello world";
+            CHECK(j.type() == json::value_t::string);
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+            CHECK(j.type() == json::value_t::number_integer);
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+            CHECK(j.type() == json::value_t::number_unsigned);
+        }
+
+        SECTION("number (floating-point)")
+        {
+            json j = 42.23;
+            CHECK(j.type() == json::value_t::number_float);
+        }
+    }
+
+    SECTION("return the type of the object (implicit)")
+    {
+        SECTION("null")
+        {
+            json j = nullptr;
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("object")
+        {
+            json j = {{"foo", "bar"}};
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("array")
+        {
+            json j = {1, 2, 3, 4};
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("boolean")
+        {
+            json j = true;
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("string")
+        {
+            json j = "Hello world";
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+
+        SECTION("number (floating-point)")
+        {
+            json j = 42.23;
+            json::value_t t = j;
+            CHECK(t == j.type());
+        }
+    }
+}

test/src/unit-iterator_wrapper.cpp

@@ -0,0 +1,729 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("iterator_wrapper")
+{
+    SECTION("object")
+    {
+        SECTION("value")
+        {
+            json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("reference")
+        {
+            json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+
+                        // change the value
+                        i.value() = json(11);
+                        CHECK(i.value() == json(11));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+
+                        // change the value
+                        i.value() = json(22);
+                        CHECK(i.value() == json(22));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+
+            // check if values where changed
+            CHECK(j == json({{"A", 11}, {"B", 22}}));
+        }
+
+        SECTION("const value")
+        {
+            json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const reference")
+        {
+            json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+    }
+
+    SECTION("const object")
+    {
+        SECTION("value")
+        {
+            const json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("reference")
+        {
+            const json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const value")
+        {
+            const json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const reference")
+        {
+            const json j = {{"A", 1}, {"B", 2}};
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "A");
+                        CHECK(i.value() == json(1));
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "B");
+                        CHECK(i.value() == json(2));
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+    }
+
+    SECTION("array")
+    {
+        SECTION("value")
+        {
+            json j = {"A", "B"};
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("reference")
+        {
+            json j = {"A", "B"};
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+
+                        // change the value
+                        i.value() = "AA";
+                        CHECK(i.value() == "AA");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+
+                        // change the value
+                        i.value() = "BB";
+                        CHECK(i.value() == "BB");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+
+            // check if values where changed
+            CHECK(j == json({"AA", "BB"}));
+        }
+
+        SECTION("const value")
+        {
+            json j = {"A", "B"};
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const reference")
+        {
+            json j = {"A", "B"};
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+    }
+
+    SECTION("const array")
+    {
+        SECTION("value")
+        {
+            const json j = {"A", "B"};
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("reference")
+        {
+            const json j = {"A", "B"};
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const value")
+        {
+            const json j = {"A", "B"};
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+
+        SECTION("const reference")
+        {
+            const json j = {"A", "B"};
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                switch (counter++)
+                {
+                    case 1:
+                    {
+                        CHECK(i.key() == "0");
+                        CHECK(i.value() == "A");
+                        break;
+                    }
+
+                    case 2:
+                    {
+                        CHECK(i.key() == "1");
+                        CHECK(i.value() == "B");
+                        break;
+                    }
+
+                    default:
+                    {
+                        break;
+                    }
+                }
+            }
+
+            CHECK(counter == 3);
+        }
+    }
+
+    SECTION("primitive")
+    {
+        SECTION("value")
+        {
+            json j = 1;
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+
+        SECTION("reference")
+        {
+            json j = 1;
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+
+                // change value
+                i.value() = json(2);
+            }
+
+            CHECK(counter == 2);
+
+            // check if value has changed
+            CHECK(j == json(2));
+        }
+
+        SECTION("const value")
+        {
+            json j = 1;
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+
+        SECTION("const reference")
+        {
+            json j = 1;
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+    }
+
+    SECTION("const primitive")
+    {
+        SECTION("value")
+        {
+            const json j = 1;
+            int counter = 1;
+
+            for (auto i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+
+        SECTION("reference")
+        {
+            const json j = 1;
+            int counter = 1;
+
+            for (auto& i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+
+        SECTION("const value")
+        {
+            const json j = 1;
+            int counter = 1;
+
+            for (const auto i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+
+        SECTION("const reference")
+        {
+            const json j = 1;
+            int counter = 1;
+
+            for (const auto& i : json::iterator_wrapper(j))
+            {
+                ++counter;
+                CHECK(i.key() == "");
+                CHECK(i.value() == json(1));
+            }
+
+            CHECK(counter == 2);
+        }
+    }
+}

test/src/unit-iterators2.cpp

@@ -0,0 +1,873 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("iterators 2")
+{
+    SECTION("iterator comparisons")
+    {
+        json j_values = {nullptr, true, 42, 42u, 23.23, {{"one", 1}, {"two", 2}}, {1, 2, 3, 4, 5}, "Hello, world"};
+
+        for (json& j : j_values)
+        {
+            auto it1 = j.begin();
+            auto it2 = j.begin();
+            auto it3 = j.begin();
+            ++it2;
+            ++it3;
+            ++it3;
+            auto it1_c = j.cbegin();
+            auto it2_c = j.cbegin();
+            auto it3_c = j.cbegin();
+            ++it2_c;
+            ++it3_c;
+            ++it3_c;
+
+            // comparison: equal
+            {
+                CHECK(it1 == it1);
+                CHECK(not (it1 == it2));
+                CHECK(not (it1 == it3));
+                CHECK(not (it2 == it3));
+                CHECK(it1_c == it1_c);
+                CHECK(not (it1_c == it2_c));
+                CHECK(not (it1_c == it3_c));
+                CHECK(not (it2_c == it3_c));
+            }
+
+            // comparison: not equal
+            {
+                // check definition
+                CHECK( (it1 != it1) == not(it1 == it1) );
+                CHECK( (it1 != it2) == not(it1 == it2) );
+                CHECK( (it1 != it3) == not(it1 == it3) );
+                CHECK( (it2 != it3) == not(it2 == it3) );
+                CHECK( (it1_c != it1_c) == not(it1_c == it1_c) );
+                CHECK( (it1_c != it2_c) == not(it1_c == it2_c) );
+                CHECK( (it1_c != it3_c) == not(it1_c == it3_c) );
+                CHECK( (it2_c != it3_c) == not(it2_c == it3_c) );
+            }
+
+            // comparison: smaller
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 < it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 < it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 < it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 < it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c < it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 < it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 < it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 < it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 < it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c < it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    CHECK(not (it1 < it1));
+                    CHECK(it1 < it2);
+                    CHECK(it1 < it3);
+                    CHECK(it2 < it3);
+                    CHECK(not (it1_c < it1_c));
+                    CHECK(it1_c < it2_c);
+                    CHECK(it1_c < it3_c);
+                    CHECK(it2_c < it3_c);
+                }
+            }
+
+            // comparison: less than or equal
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 <= it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 <= it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 <= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 <= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c <= it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 <= it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 <= it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 <= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 <= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c <= it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 <= it1) == not(it1 < it1) );
+                    CHECK( (it1 <= it2) == not(it2 < it1) );
+                    CHECK( (it1 <= it3) == not(it3 < it1) );
+                    CHECK( (it2 <= it3) == not(it3 < it2) );
+                    CHECK( (it1_c <= it1_c) == not(it1_c < it1_c) );
+                    CHECK( (it1_c <= it2_c) == not(it2_c < it1_c) );
+                    CHECK( (it1_c <= it3_c) == not(it3_c < it1_c) );
+                    CHECK( (it2_c <= it3_c) == not(it3_c < it2_c) );
+                }
+            }
+
+            // comparison: greater than
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 > it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 > it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 > it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 > it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c > it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 > it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 > it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 > it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 > it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c > it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 > it1) == (it1 < it1) );
+                    CHECK( (it1 > it2) == (it2 < it1) );
+                    CHECK( (it1 > it3) == (it3 < it1) );
+                    CHECK( (it2 > it3) == (it3 < it2) );
+                    CHECK( (it1_c > it1_c) == (it1_c < it1_c) );
+                    CHECK( (it1_c > it2_c) == (it2_c < it1_c) );
+                    CHECK( (it1_c > it3_c) == (it3_c < it1_c) );
+                    CHECK( (it2_c > it3_c) == (it3_c < it2_c) );
+                }
+            }
+
+            // comparison: greater than or equal
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 >= it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 >= it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 >= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 >= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c >= it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 >= it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 >= it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 >= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 >= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c >= it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 >= it1) == not(it1 < it1) );
+                    CHECK( (it1 >= it2) == not(it1 < it2) );
+                    CHECK( (it1 >= it3) == not(it1 < it3) );
+                    CHECK( (it2 >= it3) == not(it2 < it3) );
+                    CHECK( (it1_c >= it1_c) == not(it1_c < it1_c) );
+                    CHECK( (it1_c >= it2_c) == not(it1_c < it2_c) );
+                    CHECK( (it1_c >= it3_c) == not(it1_c < it3_c) );
+                    CHECK( (it2_c >= it3_c) == not(it2_c < it3_c) );
+                }
+            }
+        }
+
+        // check exceptions if different objects are compared
+        for (auto j : j_values)
+        {
+            for (auto k : j_values)
+            {
+                if (j != k)
+                {
+                    CHECK_THROWS_AS(j.begin() == k.begin(), std::domain_error);
+                    CHECK_THROWS_AS(j.cbegin() == k.cbegin(), std::domain_error);
+                    CHECK_THROWS_WITH(j.begin() == k.begin(), "cannot compare iterators of different containers");
+                    CHECK_THROWS_WITH(j.cbegin() == k.cbegin(), "cannot compare iterators of different containers");
+
+                    CHECK_THROWS_AS(j.begin() < k.begin(), std::domain_error);
+                    CHECK_THROWS_AS(j.cbegin() < k.cbegin(), std::domain_error);
+                    CHECK_THROWS_WITH(j.begin() < k.begin(), "cannot compare iterators of different containers");
+                    CHECK_THROWS_WITH(j.cbegin() < k.cbegin(), "cannot compare iterators of different containers");
+                }
+            }
+        }
+    }
+
+    SECTION("iterator arithmetic")
+    {
+        json j_object = {{"one", 1}, {"two", 2}, {"three", 3}};
+        json j_array = {1, 2, 3, 4, 5, 6};
+        json j_null = nullptr;
+        json j_value = 42;
+
+        SECTION("addition and subtraction")
+        {
+            SECTION("object")
+            {
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it += 1, std::domain_error);
+                    CHECK_THROWS_WITH(it += 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it += 1, std::domain_error);
+                    CHECK_THROWS_WITH(it += 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it + 1, std::domain_error);
+                    CHECK_THROWS_WITH(it + 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it + 1, std::domain_error);
+                    CHECK_THROWS_WITH(it + 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it -= 1, std::domain_error);
+                    CHECK_THROWS_WITH(it -= 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it -= 1, std::domain_error);
+                    CHECK_THROWS_WITH(it -= 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it - 1, std::domain_error);
+                    CHECK_THROWS_WITH(it - 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it - 1, std::domain_error);
+                    CHECK_THROWS_WITH(it - 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it - it, std::domain_error);
+                    CHECK_THROWS_WITH(it - it, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it - it, std::domain_error);
+                    CHECK_THROWS_WITH(it - it, "cannot use offsets with object iterators");
+                }
+            }
+
+            SECTION("array")
+            {
+                {
+                    auto it = j_array.begin();
+                    it += 3;
+                    CHECK((j_array.begin() + 3) == it);
+                    CHECK((it - 3) == j_array.begin());
+                    CHECK((it - j_array.begin()) == 3);
+                    CHECK(*it == json(4));
+                    it -= 2;
+                    CHECK(*it == json(2));
+                }
+                {
+                    auto it = j_array.cbegin();
+                    it += 3;
+                    CHECK((j_array.cbegin() + 3) == it);
+                    CHECK((it - 3) == j_array.cbegin());
+                    CHECK((it - j_array.cbegin()) == 3);
+                    CHECK(*it == json(4));
+                    it -= 2;
+                    CHECK(*it == json(2));
+                }
+            }
+
+            SECTION("null")
+            {
+                {
+                    auto it = j_null.begin();
+                    it += 3;
+                    CHECK((j_null.begin() + 3) == it);
+                    CHECK((it - 3) == j_null.begin());
+                    CHECK((it - j_null.begin()) == 3);
+                    CHECK(it != j_null.end());
+                    it -= 3;
+                    CHECK(it == j_null.end());
+                }
+                {
+                    auto it = j_null.cbegin();
+                    it += 3;
+                    CHECK((j_null.cbegin() + 3) == it);
+                    CHECK((it - 3) == j_null.cbegin());
+                    CHECK((it - j_null.cbegin()) == 3);
+                    CHECK(it != j_null.cend());
+                    it -= 3;
+                    CHECK(it == j_null.cend());
+                }
+            }
+
+            SECTION("value")
+            {
+                {
+                    auto it = j_value.begin();
+                    it += 3;
+                    CHECK((j_value.begin() + 3) == it);
+                    CHECK((it - 3) == j_value.begin());
+                    CHECK((it - j_value.begin()) == 3);
+                    CHECK(it != j_value.end());
+                    it -= 3;
+                    CHECK(*it == json(42));
+                }
+                {
+                    auto it = j_value.cbegin();
+                    it += 3;
+                    CHECK((j_value.cbegin() + 3) == it);
+                    CHECK((it - 3) == j_value.cbegin());
+                    CHECK((it - j_value.cbegin()) == 3);
+                    CHECK(it != j_value.cend());
+                    it -= 3;
+                    CHECK(*it == json(42));
+                }
+            }
+        }
+
+        SECTION("subscript operator")
+        {
+            SECTION("object")
+            {
+                {
+                    auto it = j_object.begin();
+                    CHECK_THROWS_AS(it[0], std::domain_error);
+                    CHECK_THROWS_AS(it[1], std::domain_error);
+                    CHECK_THROWS_WITH(it[0], "cannot use operator[] for object iterators");
+                    CHECK_THROWS_WITH(it[1], "cannot use operator[] for object iterators");
+                }
+                {
+                    auto it = j_object.cbegin();
+                    CHECK_THROWS_AS(it[0], std::domain_error);
+                    CHECK_THROWS_AS(it[1], std::domain_error);
+                    CHECK_THROWS_WITH(it[0], "cannot use operator[] for object iterators");
+                    CHECK_THROWS_WITH(it[1], "cannot use operator[] for object iterators");
+                }
+            }
+
+            SECTION("array")
+            {
+                {
+                    auto it = j_array.begin();
+                    CHECK(it[0] == json(1));
+                    CHECK(it[1] == json(2));
+                    CHECK(it[2] == json(3));
+                    CHECK(it[3] == json(4));
+                    CHECK(it[4] == json(5));
+                    CHECK(it[5] == json(6));
+                }
+                {
+                    auto it = j_array.cbegin();
+                    CHECK(it[0] == json(1));
+                    CHECK(it[1] == json(2));
+                    CHECK(it[2] == json(3));
+                    CHECK(it[3] == json(4));
+                    CHECK(it[4] == json(5));
+                    CHECK(it[5] == json(6));
+                }
+            }
+
+            SECTION("null")
+            {
+                {
+                    auto it = j_null.begin();
+                    CHECK_THROWS_AS(it[0], std::out_of_range);
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[0], "cannot get value");
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+                {
+                    auto it = j_null.cbegin();
+                    CHECK_THROWS_AS(it[0], std::out_of_range);
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[0], "cannot get value");
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+            }
+
+            SECTION("value")
+            {
+                {
+                    auto it = j_value.begin();
+                    CHECK(it[0] == json(42));
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+                {
+                    auto it = j_value.cbegin();
+                    CHECK(it[0] == json(42));
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+            }
+        }
+    }
+
+    SECTION("reverse iterator comparisons")
+    {
+        json j_values = {nullptr, true, 42, 42u, 23.23, {{"one", 1}, {"two", 2}}, {1, 2, 3, 4, 5}, "Hello, world"};
+
+        for (json& j : j_values)
+        {
+            auto it1 = j.rbegin();
+            auto it2 = j.rbegin();
+            auto it3 = j.rbegin();
+            ++it2;
+            ++it3;
+            ++it3;
+            auto it1_c = j.crbegin();
+            auto it2_c = j.crbegin();
+            auto it3_c = j.crbegin();
+            ++it2_c;
+            ++it3_c;
+            ++it3_c;
+
+            // comparison: equal
+            {
+                CHECK(it1 == it1);
+                CHECK(not (it1 == it2));
+                CHECK(not (it1 == it3));
+                CHECK(not (it2 == it3));
+                CHECK(it1_c == it1_c);
+                CHECK(not (it1_c == it2_c));
+                CHECK(not (it1_c == it3_c));
+                CHECK(not (it2_c == it3_c));
+            }
+
+            // comparison: not equal
+            {
+                // check definition
+                CHECK( (it1 != it1) == not(it1 == it1) );
+                CHECK( (it1 != it2) == not(it1 == it2) );
+                CHECK( (it1 != it3) == not(it1 == it3) );
+                CHECK( (it2 != it3) == not(it2 == it3) );
+                CHECK( (it1_c != it1_c) == not(it1_c == it1_c) );
+                CHECK( (it1_c != it2_c) == not(it1_c == it2_c) );
+                CHECK( (it1_c != it3_c) == not(it1_c == it3_c) );
+                CHECK( (it2_c != it3_c) == not(it2_c == it3_c) );
+            }
+
+            // comparison: smaller
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 < it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 < it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 < it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 < it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c < it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c < it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 < it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 < it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 < it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 < it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c < it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c < it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    CHECK(not (it1 < it1));
+                    CHECK(it1 < it2);
+                    CHECK(it1 < it3);
+                    CHECK(it2 < it3);
+                    CHECK(not (it1_c < it1_c));
+                    CHECK(it1_c < it2_c);
+                    CHECK(it1_c < it3_c);
+                    CHECK(it2_c < it3_c);
+                }
+            }
+
+            // comparison: less than or equal
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 <= it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 <= it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 <= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 <= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c <= it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c <= it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 <= it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 <= it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 <= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 <= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c <= it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c <= it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 <= it1) == not(it1 < it1) );
+                    CHECK( (it1 <= it2) == not(it2 < it1) );
+                    CHECK( (it1 <= it3) == not(it3 < it1) );
+                    CHECK( (it2 <= it3) == not(it3 < it2) );
+                    CHECK( (it1_c <= it1_c) == not(it1_c < it1_c) );
+                    CHECK( (it1_c <= it2_c) == not(it2_c < it1_c) );
+                    CHECK( (it1_c <= it3_c) == not(it3_c < it1_c) );
+                    CHECK( (it2_c <= it3_c) == not(it3_c < it2_c) );
+                }
+            }
+
+            // comparison: greater than
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 > it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 > it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 > it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 > it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c > it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c > it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 > it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 > it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 > it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 > it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c > it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c > it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 > it1) == (it1 < it1) );
+                    CHECK( (it1 > it2) == (it2 < it1) );
+                    CHECK( (it1 > it3) == (it3 < it1) );
+                    CHECK( (it2 > it3) == (it3 < it2) );
+                    CHECK( (it1_c > it1_c) == (it1_c < it1_c) );
+                    CHECK( (it1_c > it2_c) == (it2_c < it1_c) );
+                    CHECK( (it1_c > it3_c) == (it3_c < it1_c) );
+                    CHECK( (it2_c > it3_c) == (it3_c < it2_c) );
+                }
+            }
+
+            // comparison: greater than or equal
+            {
+                if (j.type() == json::value_t::object)
+                {
+                    CHECK_THROWS_AS(it1 >= it1, std::domain_error);
+                    CHECK_THROWS_AS(it1 >= it2, std::domain_error);
+                    CHECK_THROWS_AS(it2 >= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1 >= it3, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it1_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it2_c, std::domain_error);
+                    CHECK_THROWS_AS(it2_c >= it3_c, std::domain_error);
+                    CHECK_THROWS_AS(it1_c >= it3_c, std::domain_error);
+                    CHECK_THROWS_WITH(it1 >= it1, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 >= it2, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2 >= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1 >= it3, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it1_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it2_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it2_c >= it3_c, "cannot compare order of object iterators");
+                    CHECK_THROWS_WITH(it1_c >= it3_c, "cannot compare order of object iterators");
+                }
+                else
+                {
+                    // check definition
+                    CHECK( (it1 >= it1) == not(it1 < it1) );
+                    CHECK( (it1 >= it2) == not(it1 < it2) );
+                    CHECK( (it1 >= it3) == not(it1 < it3) );
+                    CHECK( (it2 >= it3) == not(it2 < it3) );
+                    CHECK( (it1_c >= it1_c) == not(it1_c < it1_c) );
+                    CHECK( (it1_c >= it2_c) == not(it1_c < it2_c) );
+                    CHECK( (it1_c >= it3_c) == not(it1_c < it3_c) );
+                    CHECK( (it2_c >= it3_c) == not(it2_c < it3_c) );
+                }
+            }
+        }
+
+        // check exceptions if different objects are compared
+        for (auto j : j_values)
+        {
+            for (auto k : j_values)
+            {
+                if (j != k)
+                {
+                    CHECK_THROWS_AS(j.rbegin() == k.rbegin(), std::domain_error);
+                    CHECK_THROWS_AS(j.crbegin() == k.crbegin(), std::domain_error);
+                    CHECK_THROWS_WITH(j.rbegin() == k.rbegin(), "cannot compare iterators of different containers");
+                    CHECK_THROWS_WITH(j.crbegin() == k.crbegin(), "cannot compare iterators of different containers");
+
+                    CHECK_THROWS_AS(j.rbegin() < k.rbegin(), std::domain_error);
+                    CHECK_THROWS_AS(j.crbegin() < k.crbegin(), std::domain_error);
+                    CHECK_THROWS_WITH(j.rbegin() < k.rbegin(), "cannot compare iterators of different containers");
+                    CHECK_THROWS_WITH(j.crbegin() < k.crbegin(), "cannot compare iterators of different containers");
+                }
+            }
+        }
+    }
+
+    SECTION("reverse iterator arithmetic")
+    {
+        json j_object = {{"one", 1}, {"two", 2}, {"three", 3}};
+        json j_array = {1, 2, 3, 4, 5, 6};
+        json j_null = nullptr;
+        json j_value = 42;
+
+        SECTION("addition and subtraction")
+        {
+            SECTION("object")
+            {
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it += 1, std::domain_error);
+                    CHECK_THROWS_WITH(it += 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it += 1, std::domain_error);
+                    CHECK_THROWS_WITH(it += 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it + 1, std::domain_error);
+                    CHECK_THROWS_WITH(it + 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it + 1, std::domain_error);
+                    CHECK_THROWS_WITH(it + 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it -= 1, std::domain_error);
+                    CHECK_THROWS_WITH(it -= 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it -= 1, std::domain_error);
+                    CHECK_THROWS_WITH(it -= 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it - 1, std::domain_error);
+                    CHECK_THROWS_WITH(it - 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it - 1, std::domain_error);
+                    CHECK_THROWS_WITH(it - 1, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it - it, std::domain_error);
+                    CHECK_THROWS_WITH(it - it, "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it - it, std::domain_error);
+                    CHECK_THROWS_WITH(it - it, "cannot use offsets with object iterators");
+                }
+            }
+
+            SECTION("array")
+            {
+                {
+                    auto it = j_array.rbegin();
+                    it += 3;
+                    CHECK((j_array.rbegin() + 3) == it);
+                    CHECK((it - 3) == j_array.rbegin());
+                    CHECK((j_array.rbegin() - it) == 3);
+                    CHECK(*it == json(3));
+                    it -= 2;
+                    CHECK(*it == json(5));
+                }
+                {
+                    auto it = j_array.crbegin();
+                    it += 3;
+                    CHECK((j_array.crbegin() + 3) == it);
+                    CHECK((it - 3) == j_array.crbegin());
+                    CHECK((j_array.crbegin() - it) == 3);
+                    CHECK(*it == json(3));
+                    it -= 2;
+                    CHECK(*it == json(5));
+                }
+            }
+
+            SECTION("null")
+            {
+                {
+                    auto it = j_null.rbegin();
+                    it += 3;
+                    CHECK((j_null.rbegin() + 3) == it);
+                    CHECK((it - 3) == j_null.rbegin());
+                    CHECK((j_null.rbegin() - it) == 3);
+                    CHECK(it != j_null.rend());
+                    it -= 3;
+                    CHECK(it == j_null.rend());
+                }
+                {
+                    auto it = j_null.crbegin();
+                    it += 3;
+                    CHECK((j_null.crbegin() + 3) == it);
+                    CHECK((it - 3) == j_null.crbegin());
+                    CHECK((j_null.crbegin() - it) == 3);
+                    CHECK(it != j_null.crend());
+                    it -= 3;
+                    CHECK(it == j_null.crend());
+                }
+            }
+
+            SECTION("value")
+            {
+                {
+                    auto it = j_value.rbegin();
+                    it += 3;
+                    CHECK((j_value.rbegin() + 3) == it);
+                    CHECK((it - 3) == j_value.rbegin());
+                    CHECK((j_value.rbegin() - it) == 3);
+                    CHECK(it != j_value.rend());
+                    it -= 3;
+                    CHECK(*it == json(42));
+                }
+                {
+                    auto it = j_value.crbegin();
+                    it += 3;
+                    CHECK((j_value.crbegin() + 3) == it);
+                    CHECK((it - 3) == j_value.crbegin());
+                    CHECK((j_value.crbegin() - it) == 3);
+                    CHECK(it != j_value.crend());
+                    it -= 3;
+                    CHECK(*it == json(42));
+                }
+            }
+        }
+
+        SECTION("subscript operator")
+        {
+            SECTION("object")
+            {
+                {
+                    auto it = j_object.rbegin();
+                    CHECK_THROWS_AS(it[0], std::domain_error);
+                    CHECK_THROWS_AS(it[1], std::domain_error);
+                    CHECK_THROWS_WITH(it[0], "cannot use offsets with object iterators");
+                    CHECK_THROWS_WITH(it[1], "cannot use offsets with object iterators");
+                }
+                {
+                    auto it = j_object.crbegin();
+                    CHECK_THROWS_AS(it[0], std::domain_error);
+                    CHECK_THROWS_AS(it[1], std::domain_error);
+                    CHECK_THROWS_WITH(it[0], "cannot use offsets with object iterators");
+                    CHECK_THROWS_WITH(it[1], "cannot use offsets with object iterators");
+                }
+            }
+
+            SECTION("array")
+            {
+                {
+                    auto it = j_array.rbegin();
+                    CHECK(it[0] == json(6));
+                    CHECK(it[1] == json(5));
+                    CHECK(it[2] == json(4));
+                    CHECK(it[3] == json(3));
+                    CHECK(it[4] == json(2));
+                    CHECK(it[5] == json(1));
+                }
+                {
+                    auto it = j_array.crbegin();
+                    CHECK(it[0] == json(6));
+                    CHECK(it[1] == json(5));
+                    CHECK(it[2] == json(4));
+                    CHECK(it[3] == json(3));
+                    CHECK(it[4] == json(2));
+                    CHECK(it[5] == json(1));
+                }
+            }
+
+            SECTION("null")
+            {
+                {
+                    auto it = j_null.rbegin();
+                    CHECK_THROWS_AS(it[0], std::out_of_range);
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[0], "cannot get value");
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+                {
+                    auto it = j_null.crbegin();
+                    CHECK_THROWS_AS(it[0], std::out_of_range);
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[0], "cannot get value");
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+            }
+
+            SECTION("value")
+            {
+                {
+                    auto it = j_value.rbegin();
+                    CHECK(it[0] == json(42));
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+                {
+                    auto it = j_value.crbegin();
+                    CHECK(it[0] == json(42));
+                    CHECK_THROWS_AS(it[1], std::out_of_range);
+                    CHECK_THROWS_WITH(it[1], "cannot get value");
+                }
+            }
+        }
+    }
+}

test/src/unit-json_pointer.cpp

@@ -0,0 +1,388 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("JSON pointers")
+{
+    SECTION("errors")
+    {
+        CHECK_THROWS_AS(json::json_pointer("foo"), std::domain_error);
+        CHECK_THROWS_WITH(json::json_pointer("foo"), "JSON pointer must be empty or begin with '/'");
+
+        CHECK_THROWS_AS(json::json_pointer("/~~"), std::domain_error);
+        CHECK_THROWS_WITH(json::json_pointer("/~~"), "escape error: '~' must be followed with '0' or '1'");
+
+        CHECK_THROWS_AS(json::json_pointer("/~"), std::domain_error);
+        CHECK_THROWS_WITH(json::json_pointer("/~"), "escape error: '~' must be followed with '0' or '1'");
+
+        json::json_pointer p;
+        CHECK_THROWS_AS(p.top(), std::domain_error);
+        CHECK_THROWS_WITH(p.top(), "JSON pointer has no parent");
+        CHECK_THROWS_AS(p.pop_back(), std::domain_error);
+        CHECK_THROWS_WITH(p.pop_back(), "JSON pointer has no parent");
+    }
+
+    SECTION("examples from RFC 6901")
+    {
+        SECTION("nonconst access")
+        {
+            json j = R"(
+            {
+                "foo": ["bar", "baz"],
+                "": 0,
+                "a/b": 1,
+                "c%d": 2,
+                "e^f": 3,
+                "g|h": 4,
+                "i\\j": 5,
+                "k\"l": 6,
+                " ": 7,
+                "m~n": 8
+            }
+            )"_json;
+
+            // the whole document
+            CHECK(j[json::json_pointer()] == j);
+            CHECK(j[json::json_pointer("")] == j);
+
+            // array access
+            CHECK(j[json::json_pointer("/foo")] == j["foo"]);
+            CHECK(j[json::json_pointer("/foo/0")] == j["foo"][0]);
+            CHECK(j[json::json_pointer("/foo/1")] == j["foo"][1]);
+            CHECK(j["/foo/1"_json_pointer] == j["foo"][1]);
+
+            // checked array access
+            CHECK(j.at(json::json_pointer("/foo/0")) == j["foo"][0]);
+            CHECK(j.at(json::json_pointer("/foo/1")) == j["foo"][1]);
+
+            // empty string access
+            CHECK(j[json::json_pointer("/")] == j[""]);
+
+            // other cases
+            CHECK(j[json::json_pointer("/ ")] == j[" "]);
+            CHECK(j[json::json_pointer("/c%d")] == j["c%d"]);
+            CHECK(j[json::json_pointer("/e^f")] == j["e^f"]);
+            CHECK(j[json::json_pointer("/g|h")] == j["g|h"]);
+            CHECK(j[json::json_pointer("/i\\j")] == j["i\\j"]);
+            CHECK(j[json::json_pointer("/k\"l")] == j["k\"l"]);
+
+            // checked access
+            CHECK(j.at(json::json_pointer("/ ")) == j[" "]);
+            CHECK(j.at(json::json_pointer("/c%d")) == j["c%d"]);
+            CHECK(j.at(json::json_pointer("/e^f")) == j["e^f"]);
+            CHECK(j.at(json::json_pointer("/g|h")) == j["g|h"]);
+            CHECK(j.at(json::json_pointer("/i\\j")) == j["i\\j"]);
+            CHECK(j.at(json::json_pointer("/k\"l")) == j["k\"l"]);
+
+            // escaped access
+            CHECK(j[json::json_pointer("/a~1b")] == j["a/b"]);
+            CHECK(j[json::json_pointer("/m~0n")] == j["m~n"]);
+
+            // unescaped access
+            CHECK_THROWS_AS(j[json::json_pointer("/a/b")], std::out_of_range);
+            CHECK_THROWS_WITH(j[json::json_pointer("/a/b")], "unresolved reference token 'b'");
+            // "/a/b" works for JSON {"a": {"b": 42}}
+            CHECK(json({{"a", {{"b", 42}}}})[json::json_pointer("/a/b")] == json(42));
+
+            // unresolved access
+            json j_primitive = 1;
+            CHECK_THROWS_AS(j_primitive["/foo"_json_pointer], std::out_of_range);
+            CHECK_THROWS_WITH(j_primitive["/foo"_json_pointer], "unresolved reference token 'foo'");
+            CHECK_THROWS_AS(j_primitive.at("/foo"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j_primitive.at("/foo"_json_pointer), "unresolved reference token 'foo'");
+        }
+
+        SECTION("const access")
+        {
+            const json j = R"(
+            {
+                "foo": ["bar", "baz"],
+                "": 0,
+                "a/b": 1,
+                "c%d": 2,
+                "e^f": 3,
+                "g|h": 4,
+                "i\\j": 5,
+                "k\"l": 6,
+                " ": 7,
+                "m~n": 8
+            }
+            )"_json;
+
+            // the whole document
+            CHECK(j[json::json_pointer()] == j);
+            CHECK(j[json::json_pointer("")] == j);
+
+            // array access
+            CHECK(j[json::json_pointer("/foo")] == j["foo"]);
+            CHECK(j[json::json_pointer("/foo/0")] == j["foo"][0]);
+            CHECK(j[json::json_pointer("/foo/1")] == j["foo"][1]);
+            CHECK(j["/foo/1"_json_pointer] == j["foo"][1]);
+
+            // checked array access
+            CHECK(j.at(json::json_pointer("/foo/0")) == j["foo"][0]);
+            CHECK(j.at(json::json_pointer("/foo/1")) == j["foo"][1]);
+
+            // empty string access
+            CHECK(j[json::json_pointer("/")] == j[""]);
+
+            // other cases
+            CHECK(j[json::json_pointer("/ ")] == j[" "]);
+            CHECK(j[json::json_pointer("/c%d")] == j["c%d"]);
+            CHECK(j[json::json_pointer("/e^f")] == j["e^f"]);
+            CHECK(j[json::json_pointer("/g|h")] == j["g|h"]);
+            CHECK(j[json::json_pointer("/i\\j")] == j["i\\j"]);
+            CHECK(j[json::json_pointer("/k\"l")] == j["k\"l"]);
+
+            // checked access
+            CHECK(j.at(json::json_pointer("/ ")) == j[" "]);
+            CHECK(j.at(json::json_pointer("/c%d")) == j["c%d"]);
+            CHECK(j.at(json::json_pointer("/e^f")) == j["e^f"]);
+            CHECK(j.at(json::json_pointer("/g|h")) == j["g|h"]);
+            CHECK(j.at(json::json_pointer("/i\\j")) == j["i\\j"]);
+            CHECK(j.at(json::json_pointer("/k\"l")) == j["k\"l"]);
+
+            // escaped access
+            CHECK(j[json::json_pointer("/a~1b")] == j["a/b"]);
+            CHECK(j[json::json_pointer("/m~0n")] == j["m~n"]);
+
+            // unescaped access
+            CHECK_THROWS_AS(j.at(json::json_pointer("/a/b")), std::out_of_range);
+            CHECK_THROWS_WITH(j.at(json::json_pointer("/a/b")), "key 'a' not found");
+
+            // unresolved access
+            const json j_primitive = 1;
+            CHECK_THROWS_AS(j_primitive["/foo"_json_pointer], std::out_of_range);
+            CHECK_THROWS_WITH(j_primitive["/foo"_json_pointer], "unresolved reference token 'foo'");
+            CHECK_THROWS_AS(j_primitive.at("/foo"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j_primitive.at("/foo"_json_pointer), "unresolved reference token 'foo'");
+        }
+
+        SECTION("user-defined string literal")
+        {
+            json j = R"(
+            {
+                "foo": ["bar", "baz"],
+                "": 0,
+                "a/b": 1,
+                "c%d": 2,
+                "e^f": 3,
+                "g|h": 4,
+                "i\\j": 5,
+                "k\"l": 6,
+                " ": 7,
+                "m~n": 8
+            }
+            )"_json;
+
+            // the whole document
+            CHECK(j[""_json_pointer] == j);
+
+            // array access
+            CHECK(j["/foo"_json_pointer] == j["foo"]);
+            CHECK(j["/foo/0"_json_pointer] == j["foo"][0]);
+            CHECK(j["/foo/1"_json_pointer] == j["foo"][1]);
+        }
+    }
+
+    SECTION("array access")
+    {
+        SECTION("nonconst access")
+        {
+            json j = {1, 2, 3};
+            const json j_const = j;
+
+            // check reading access
+            CHECK(j["/0"_json_pointer] == j[0]);
+            CHECK(j["/1"_json_pointer] == j[1]);
+            CHECK(j["/2"_json_pointer] == j[2]);
+
+            // assign to existing index
+            j["/1"_json_pointer] = 13;
+            CHECK(j[1] == json(13));
+
+            // assign to nonexisting index
+            j["/3"_json_pointer] = 33;
+            CHECK(j[3] == json(33));
+
+            // assign to nonexisting index (with gap)
+            j["/5"_json_pointer] = 55;
+            CHECK(j == json({1, 13, 3, 33, nullptr, 55}));
+
+            // error with leading 0
+            CHECK_THROWS_AS(j["/01"_json_pointer], std::domain_error);
+            CHECK_THROWS_WITH(j["/01"_json_pointer], "array index must not begin with '0'");
+            CHECK_THROWS_AS(j_const["/01"_json_pointer], std::domain_error);
+            CHECK_THROWS_WITH(j_const["/01"_json_pointer], "array index must not begin with '0'");
+            CHECK_THROWS_AS(j.at("/01"_json_pointer), std::domain_error);
+            CHECK_THROWS_WITH(j.at("/01"_json_pointer), "array index must not begin with '0'");
+            CHECK_THROWS_AS(j_const.at("/01"_json_pointer), std::domain_error);
+            CHECK_THROWS_WITH(j_const.at("/01"_json_pointer), "array index must not begin with '0'");
+
+            // error with incorrect numbers
+            CHECK_THROWS_AS(j["/one"_json_pointer] = 1, std::invalid_argument);
+
+            // assign to "-"
+            j["/-"_json_pointer] = 99;
+            CHECK(j == json({1, 13, 3, 33, nullptr, 55, 99}));
+
+            // error when using "-" in const object
+            CHECK_THROWS_AS(j_const["/-"_json_pointer], std::out_of_range);
+            CHECK_THROWS_WITH(j_const["/-"_json_pointer], "array index '-' (3) is out of range");
+
+            // error when using "-" with at
+            CHECK_THROWS_AS(j.at("/-"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j.at("/-"_json_pointer), "array index '-' (7) is out of range");
+            CHECK_THROWS_AS(j_const.at("/-"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j_const.at("/-"_json_pointer), "array index '-' (3) is out of range");
+        }
+
+        SECTION("const access")
+        {
+            const json j = {1, 2, 3};
+
+            // check reading access
+            CHECK(j["/0"_json_pointer] == j[0]);
+            CHECK(j["/1"_json_pointer] == j[1]);
+            CHECK(j["/2"_json_pointer] == j[2]);
+
+            // assign to nonexisting index
+            CHECK_THROWS_AS(j.at("/3"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j.at("/3"_json_pointer), "array index 3 is out of range");
+
+            // assign to nonexisting index (with gap)
+            CHECK_THROWS_AS(j.at("/5"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j.at("/5"_json_pointer), "array index 5 is out of range");
+
+            // assign to "-"
+            CHECK_THROWS_AS(j["/-"_json_pointer], std::out_of_range);
+            CHECK_THROWS_WITH(j["/-"_json_pointer], "array index '-' (3) is out of range");
+            CHECK_THROWS_AS(j.at("/-"_json_pointer), std::out_of_range);
+            CHECK_THROWS_WITH(j.at("/-"_json_pointer), "array index '-' (3) is out of range");
+        }
+
+    }
+
+    SECTION("flatten")
+    {
+        json j =
+        {
+            {"pi", 3.141},
+            {"happy", true},
+            {"name", "Niels"},
+            {"nothing", nullptr},
+            {
+                "answer", {
+                    {"everything", 42}
+                }
+            },
+            {"list", {1, 0, 2}},
+            {
+                "object", {
+                    {"currency", "USD"},
+                    {"value", 42.99},
+                    {"", "empty string"},
+                    {"/", "slash"},
+                    {"~", "tilde"},
+                    {"~1", "tilde1"}
+                }
+            }
+        };
+
+        json j_flatten =
+        {
+            {"/pi", 3.141},
+            {"/happy", true},
+            {"/name", "Niels"},
+            {"/nothing", nullptr},
+            {"/answer/everything", 42},
+            {"/list/0", 1},
+            {"/list/1", 0},
+            {"/list/2", 2},
+            {"/object/currency", "USD"},
+            {"/object/value", 42.99},
+            {"/object/", "empty string"},
+            {"/object/~1", "slash"},
+            {"/object/~0", "tilde"},
+            {"/object/~01", "tilde1"}
+        };
+
+        // check if flattened result is as expected
+        CHECK(j.flatten() == j_flatten);
+
+        // check if unflattened result is as expected
+        CHECK(j_flatten.unflatten() == j);
+
+        // error for nonobjects
+        CHECK_THROWS_AS(json(1).unflatten(), std::domain_error);
+        CHECK_THROWS_WITH(json(1).unflatten(), "only objects can be unflattened");
+
+        // error for nonprimitve values
+        CHECK_THROWS_AS(json({{"/1", {1, 2, 3}}}).unflatten(), std::domain_error);
+        CHECK_THROWS_WITH(json({{"/1", {1, 2, 3}}}).unflatten(), "values in object must be primitive");
+
+        // error for conflicting values
+        json j_error = {{"", 42}, {"/foo", 17}};
+        CHECK_THROWS_AS(j_error.unflatten(), std::domain_error);
+        CHECK_THROWS_WITH(j_error.unflatten(), "invalid value to unflatten");
+
+        // explicit roundtrip check
+        CHECK(j.flatten().unflatten() == j);
+
+        // roundtrip for primitive values
+        json j_null;
+        CHECK(j_null.flatten().unflatten() == j_null);
+        json j_number = 42;
+        CHECK(j_number.flatten().unflatten() == j_number);
+        json j_boolean = false;
+        CHECK(j_boolean.flatten().unflatten() == j_boolean);
+        json j_string = "foo";
+        CHECK(j_string.flatten().unflatten() == j_string);
+
+        // roundtrip for empty structured values (will be unflattened to null)
+        json j_array(json::value_t::array);
+        CHECK(j_array.flatten().unflatten() == json());
+        json j_object(json::value_t::object);
+        CHECK(j_object.flatten().unflatten() == json());
+    }
+
+    SECTION("string representation")
+    {
+        for (auto ptr :
+                {"", "/foo", "/foo/0", "/", "/a~1b", "/c%d", "/e^f", "/g|h", "/i\\j", "/k\"l", "/ ", "/m~0n"
+                })
+        {
+            CHECK(json::json_pointer(ptr).to_string() == ptr);
+        }
+    }
+}

test/src/unit-modifiers.cpp

@@ -0,0 +1,713 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("modifiers")
+{
+    SECTION("clear()")
+    {
+        SECTION("boolean")
+        {
+            json j = true;
+
+            j.clear();
+            CHECK(j == json(json::value_t::boolean));
+        }
+
+        SECTION("string")
+        {
+            json j = "hello world";
+
+            j.clear();
+            CHECK(j == json(json::value_t::string));
+        }
+
+        SECTION("array")
+        {
+            SECTION("empty array")
+            {
+                json j = json::array();
+
+                j.clear();
+                CHECK(j.empty());
+                CHECK(j == json(json::value_t::array));
+            }
+
+            SECTION("filled array")
+            {
+                json j = {1, 2, 3};
+
+                j.clear();
+                CHECK(j.empty());
+                CHECK(j == json(json::value_t::array));
+            }
+        }
+
+        SECTION("object")
+        {
+            SECTION("empty object")
+            {
+                json j = json::object();
+
+                j.clear();
+                CHECK(j.empty());
+                CHECK(j == json(json::value_t::object));
+            }
+
+            SECTION("filled object")
+            {
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+
+                j.clear();
+                CHECK(j.empty());
+                CHECK(j == json(json::value_t::object));
+            }
+        }
+
+        SECTION("number (integer)")
+        {
+            json j = 23;
+
+            j.clear();
+            CHECK(j == json(json::value_t::number_integer));
+        }
+
+        SECTION("number (unsigned)")
+        {
+            json j = 23u;
+
+            j.clear();
+            CHECK(j == json(json::value_t::number_integer));
+        }
+
+        SECTION("number (float)")
+        {
+            json j = 23.42;
+
+            j.clear();
+            CHECK(j == json(json::value_t::number_float));
+        }
+
+        SECTION("null")
+        {
+            json j = nullptr;
+
+            j.clear();
+            CHECK(j == json(json::value_t::null));
+        }
+    }
+
+    SECTION("push_back()")
+    {
+        SECTION("to array")
+        {
+            SECTION("json&&")
+            {
+                SECTION("null")
+                {
+                    json j;
+                    j.push_back(1);
+                    j.push_back(2);
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2}));
+                }
+
+                SECTION("array")
+                {
+                    json j = {1, 2, 3};
+                    j.push_back("Hello");
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2, 3, "Hello"}));
+                }
+
+                SECTION("other type")
+                {
+                    json j = 1;
+                    CHECK_THROWS_AS(j.push_back("Hello"), std::domain_error);
+                    CHECK_THROWS_WITH(j.push_back("Hello"), "cannot use push_back() with number");
+                }
+            }
+
+            SECTION("const json&")
+            {
+                SECTION("null")
+                {
+                    json j;
+                    json k(1);
+                    j.push_back(k);
+                    j.push_back(k);
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 1}));
+                }
+
+                SECTION("array")
+                {
+                    json j = {1, 2, 3};
+                    json k("Hello");
+                    j.push_back(k);
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2, 3, "Hello"}));
+                }
+
+                SECTION("other type")
+                {
+                    json j = 1;
+                    json k("Hello");
+                    CHECK_THROWS_AS(j.push_back(k), std::domain_error);
+                    CHECK_THROWS_WITH(j.push_back(k), "cannot use push_back() with number");
+                }
+            }
+        }
+
+        SECTION("to object")
+        {
+            SECTION("null")
+            {
+                json j;
+                j.push_back(json::object_t::value_type({"one", 1}));
+                j.push_back(json::object_t::value_type({"two", 2}));
+                CHECK(j.type() == json::value_t::object);
+                CHECK(j.size() == 2);
+                CHECK(j["one"] == json(1));
+                CHECK(j["two"] == json(2));
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                j.push_back(json::object_t::value_type({"one", 1}));
+                j.push_back(json::object_t::value_type({"two", 2}));
+                CHECK(j.size() == 2);
+                CHECK(j["one"] == json(1));
+                CHECK(j["two"] == json(2));
+            }
+
+            SECTION("other type")
+            {
+                json j = 1;
+                json k("Hello");
+                CHECK_THROWS_AS(j.push_back(json::object_t::value_type({"one", 1})), std::domain_error);
+                CHECK_THROWS_WITH(j.push_back(json::object_t::value_type({"one", 1})),
+                                  "cannot use push_back() with number");
+            }
+        }
+
+        SECTION("with initializer_list")
+        {
+            SECTION("null")
+            {
+                json j;
+                j.push_back({"foo", "bar"});
+                CHECK(j == json::array({{"foo", "bar"}}));
+
+                json k;
+                k.push_back({1, 2, 3});
+                CHECK(k == json::array({{1, 2, 3}}));
+            }
+
+            SECTION("array")
+            {
+                json j = {1, 2, 3};
+                j.push_back({"foo", "bar"});
+                CHECK(j == json({1, 2, 3, {"foo", "bar"}}));
+
+                json k = {1, 2, 3};
+                k.push_back({1, 2, 3});
+                CHECK(k == json({1, 2, 3, {1, 2, 3}}));
+            }
+
+            SECTION("object")
+            {
+                json j = {{"key1", 1}};
+                j.push_back({"key2", "bar"});
+                CHECK(j == json({{"key1", 1}, {"key2", "bar"}}));
+
+                json k = {{"key1", 1}};
+                CHECK_THROWS_AS(k.push_back({1, 2, 3, 4}), std::domain_error);
+                CHECK_THROWS_WITH(k.push_back({1, 2, 3, 4}), "cannot use push_back() with object");
+            }
+        }
+    }
+
+    SECTION("operator+=")
+    {
+        SECTION("to array")
+        {
+            SECTION("json&&")
+            {
+                SECTION("null")
+                {
+                    json j;
+                    j += 1;
+                    j += 2;
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2}));
+                }
+
+                SECTION("array")
+                {
+                    json j = {1, 2, 3};
+                    j += "Hello";
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2, 3, "Hello"}));
+                }
+
+                SECTION("other type")
+                {
+                    json j = 1;
+                    CHECK_THROWS_AS(j += "Hello", std::domain_error);
+                    CHECK_THROWS_WITH(j += "Hello", "cannot use push_back() with number");
+                }
+            }
+
+            SECTION("const json&")
+            {
+                SECTION("null")
+                {
+                    json j;
+                    json k(1);
+                    j += k;
+                    j += k;
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 1}));
+                }
+
+                SECTION("array")
+                {
+                    json j = {1, 2, 3};
+                    json k("Hello");
+                    j += k;
+                    CHECK(j.type() == json::value_t::array);
+                    CHECK(j == json({1, 2, 3, "Hello"}));
+                }
+
+                SECTION("other type")
+                {
+                    json j = 1;
+                    json k("Hello");
+                    CHECK_THROWS_AS(j += k, std::domain_error);
+                    CHECK_THROWS_WITH(j += k, "cannot use push_back() with number");
+                }
+            }
+        }
+
+        SECTION("to object")
+        {
+            SECTION("null")
+            {
+                json j;
+                j += json::object_t::value_type({"one", 1});
+                j += json::object_t::value_type({"two", 2});
+                CHECK(j.type() == json::value_t::object);
+                CHECK(j.size() == 2);
+                CHECK(j["one"] == json(1));
+                CHECK(j["two"] == json(2));
+            }
+
+            SECTION("object")
+            {
+                json j(json::value_t::object);
+                j += json::object_t::value_type({"one", 1});
+                j += json::object_t::value_type({"two", 2});
+                CHECK(j.size() == 2);
+                CHECK(j["one"] == json(1));
+                CHECK(j["two"] == json(2));
+            }
+
+            SECTION("other type")
+            {
+                json j = 1;
+                json k("Hello");
+                CHECK_THROWS_AS(j += json::object_t::value_type({"one", 1}), std::domain_error);
+                CHECK_THROWS_WITH(j += json::object_t::value_type({"one", 1}),
+                                  "cannot use push_back() with number");
+            }
+        }
+
+        SECTION("with initializer_list")
+        {
+            SECTION("null")
+            {
+                json j;
+                j += {"foo", "bar"};
+                CHECK(j == json::array({{"foo", "bar"}}));
+
+                json k;
+                k += {1, 2, 3};
+                CHECK(k == json::array({{1, 2, 3}}));
+            }
+
+            SECTION("array")
+            {
+                json j = {1, 2, 3};
+                j += {"foo", "bar"};
+                CHECK(j == json({1, 2, 3, {"foo", "bar"}}));
+
+                json k = {1, 2, 3};
+                k += {1, 2, 3};
+                CHECK(k == json({1, 2, 3, {1, 2, 3}}));
+            }
+
+            SECTION("object")
+            {
+                json j = {{"key1", 1}};
+                j += {"key2", "bar"};
+                CHECK(j == json({{"key1", 1}, {"key2", "bar"}}));
+
+                json k = {{"key1", 1}};
+                CHECK_THROWS_AS((k += {1, 2, 3, 4}), std::domain_error);
+                CHECK_THROWS_WITH((k += {1, 2, 3, 4}), "cannot use push_back() with object");
+            }
+        }
+    }
+
+    SECTION("insert")
+    {
+        json j_array = {1, 2, 3, 4};
+        json j_value = 5;
+
+        SECTION("value at position")
+        {
+            SECTION("insert before begin()")
+            {
+                auto it = j_array.insert(j_array.begin(), j_value);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK(j_array.begin() == it);
+                CHECK(j_array == json({5, 1, 2, 3, 4}));
+            }
+
+            SECTION("insert in the middle")
+            {
+                auto it = j_array.insert(j_array.begin() + 2, j_value);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK((it - j_array.begin()) == 2);
+                CHECK(j_array == json({1, 2, 5, 3, 4}));
+            }
+
+            SECTION("insert before end()")
+            {
+                auto it = j_array.insert(j_array.end(), j_value);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK((j_array.end() - it) == 1);
+                CHECK(j_array == json({1, 2, 3, 4, 5}));
+            }
+        }
+
+        SECTION("rvalue at position")
+        {
+            SECTION("insert before begin()")
+            {
+                auto it = j_array.insert(j_array.begin(), 5);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK(j_array.begin() == it);
+                CHECK(j_array == json({5, 1, 2, 3, 4}));
+            }
+
+            SECTION("insert in the middle")
+            {
+                auto it = j_array.insert(j_array.begin() + 2, 5);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK((it - j_array.begin()) == 2);
+                CHECK(j_array == json({1, 2, 5, 3, 4}));
+            }
+
+            SECTION("insert before end()")
+            {
+                auto it = j_array.insert(j_array.end(), 5);
+                CHECK(j_array.size() == 5);
+                CHECK(*it == j_value);
+                CHECK((j_array.end() - it) == 1);
+                CHECK(j_array == json({1, 2, 3, 4, 5}));
+            }
+        }
+
+        SECTION("copies at position")
+        {
+            SECTION("insert before begin()")
+            {
+                auto it = j_array.insert(j_array.begin(), 3, 5);
+                CHECK(j_array.size() == 7);
+                CHECK(*it == j_value);
+                CHECK(j_array.begin() == it);
+                CHECK(j_array == json({5, 5, 5, 1, 2, 3, 4}));
+            }
+
+            SECTION("insert in the middle")
+            {
+                auto it = j_array.insert(j_array.begin() + 2, 3, 5);
+                CHECK(j_array.size() == 7);
+                CHECK(*it == j_value);
+                CHECK((it - j_array.begin()) == 2);
+                CHECK(j_array == json({1, 2, 5, 5, 5, 3, 4}));
+            }
+
+            SECTION("insert before end()")
+            {
+                auto it = j_array.insert(j_array.end(), 3, 5);
+                CHECK(j_array.size() == 7);
+                CHECK(*it == j_value);
+                CHECK((j_array.end() - it) == 3);
+                CHECK(j_array == json({1, 2, 3, 4, 5, 5, 5}));
+            }
+
+            SECTION("insert nothing (count = 0)")
+            {
+                auto pos = j_array.end();
+                auto it = j_array.insert(j_array.end(), 0, 5);
+                CHECK(j_array.size() == 4);
+                CHECK(it == pos);
+                CHECK(j_array == json({1, 2, 3, 4}));
+            }
+        }
+
+        SECTION("range")
+        {
+            json j_other_array = {"first", "second"};
+
+            SECTION("proper usage")
+            {
+                auto it = j_array.insert(j_array.end(), j_other_array.begin(), j_other_array.end());
+                CHECK(j_array.size() == 6);
+                CHECK(*it == *j_other_array.begin());
+                CHECK((j_array.end() - it) == 2);
+                CHECK(j_array == json({1, 2, 3, 4, "first", "second"}));
+            }
+
+            SECTION("empty range")
+            {
+                auto it = j_array.insert(j_array.end(), j_other_array.begin(), j_other_array.begin());
+                CHECK(j_array.size() == 4);
+                CHECK(it == j_array.end());
+                CHECK(j_array == json({1, 2, 3, 4}));
+            }
+
+            SECTION("invalid iterators")
+            {
+                json j_other_array2 = {"first", "second"};
+
+                CHECK_THROWS_AS(j_array.insert(j_array.end(), j_array.begin(), j_array.end()), std::domain_error);
+                CHECK_THROWS_AS(j_array.insert(j_array.end(), j_other_array.begin(), j_other_array2.end()),
+                                std::domain_error);
+
+                CHECK_THROWS_WITH(j_array.insert(j_array.end(), j_array.begin(), j_array.end()),
+                                  "passed iterators may not belong to container");
+                CHECK_THROWS_WITH(j_array.insert(j_array.end(), j_other_array.begin(), j_other_array2.end()),
+                                  "iterators do not fit");
+            }
+        }
+
+        SECTION("initializer list at position")
+        {
+            SECTION("insert before begin()")
+            {
+                auto it = j_array.insert(j_array.begin(), {7, 8, 9});
+                CHECK(j_array.size() == 7);
+                CHECK(*it == json(7));
+                CHECK(j_array.begin() == it);
+                CHECK(j_array == json({7, 8, 9, 1, 2, 3, 4}));
+            }
+
+            SECTION("insert in the middle")
+            {
+                auto it = j_array.insert(j_array.begin() + 2, {7, 8, 9});
+                CHECK(j_array.size() == 7);
+                CHECK(*it == json(7));
+                CHECK((it - j_array.begin()) == 2);
+                CHECK(j_array == json({1, 2, 7, 8, 9, 3, 4}));
+            }
+
+            SECTION("insert before end()")
+            {
+                auto it = j_array.insert(j_array.end(), {7, 8, 9});
+                CHECK(j_array.size() == 7);
+                CHECK(*it == json(7));
+                CHECK((j_array.end() - it) == 3);
+                CHECK(j_array == json({1, 2, 3, 4, 7, 8, 9}));
+            }
+        }
+
+        SECTION("invalid iterator")
+        {
+            // pass iterator to a different array
+            json j_another_array = {1, 2};
+            json j_yet_another_array = {"first", "second"};
+            CHECK_THROWS_AS(j_array.insert(j_another_array.end(), 10), std::domain_error);
+            CHECK_THROWS_AS(j_array.insert(j_another_array.end(), j_value), std::domain_error);
+            CHECK_THROWS_AS(j_array.insert(j_another_array.end(), 10, 11), std::domain_error);
+            CHECK_THROWS_AS(j_array.insert(j_another_array.end(), j_yet_another_array.begin(),
+                                           j_yet_another_array.end()), std::domain_error);
+            CHECK_THROWS_AS(j_array.insert(j_another_array.end(), {1, 2, 3, 4}), std::domain_error);
+
+            CHECK_THROWS_WITH(j_array.insert(j_another_array.end(), 10), "iterator does not fit current value");
+            CHECK_THROWS_WITH(j_array.insert(j_another_array.end(), j_value),
+                              "iterator does not fit current value");
+            CHECK_THROWS_WITH(j_array.insert(j_another_array.end(), 10, 11),
+                              "iterator does not fit current value");
+            CHECK_THROWS_WITH(j_array.insert(j_another_array.end(), j_yet_another_array.begin(),
+                                             j_yet_another_array.end()), "iterator does not fit current value");
+            CHECK_THROWS_WITH(j_array.insert(j_another_array.end(), {1, 2, 3, 4}),
+                              "iterator does not fit current value");
+        }
+
+        SECTION("non-array type")
+        {
+            // call insert on a non-array type
+            json j_nonarray = 3;
+            json j_yet_another_array = {"first", "second"};
+            CHECK_THROWS_AS(j_nonarray.insert(j_nonarray.end(), 10), std::domain_error);
+            CHECK_THROWS_AS(j_nonarray.insert(j_nonarray.end(), j_value), std::domain_error);
+            CHECK_THROWS_AS(j_nonarray.insert(j_nonarray.end(), 10, 11), std::domain_error);
+            CHECK_THROWS_AS(j_nonarray.insert(j_nonarray.end(), j_yet_another_array.begin(),
+                                              j_yet_another_array.end()), std::domain_error);
+            CHECK_THROWS_AS(j_nonarray.insert(j_nonarray.end(), {1, 2, 3, 4}), std::domain_error);
+
+            CHECK_THROWS_WITH(j_nonarray.insert(j_nonarray.end(), 10), "cannot use insert() with number");
+            CHECK_THROWS_WITH(j_nonarray.insert(j_nonarray.end(), j_value), "cannot use insert() with number");
+            CHECK_THROWS_WITH(j_nonarray.insert(j_nonarray.end(), 10, 11), "cannot use insert() with number");
+            CHECK_THROWS_WITH(j_nonarray.insert(j_nonarray.end(), j_yet_another_array.begin(),
+                                                j_yet_another_array.end()), "cannot use insert() with number");
+            CHECK_THROWS_WITH(j_nonarray.insert(j_nonarray.end(), {1, 2, 3, 4}),
+                              "cannot use insert() with number");
+        }
+    }
+
+    SECTION("swap()")
+    {
+        SECTION("json")
+        {
+            SECTION("member swap")
+            {
+                json j("hello world");
+                json k(42.23);
+
+                j.swap(k);
+
+                CHECK(j == json(42.23));
+                CHECK(k == json("hello world"));
+            }
+
+            SECTION("nonmember swap")
+            {
+                json j("hello world");
+                json k(42.23);
+
+                std::swap(j, k);
+
+                CHECK(j == json(42.23));
+                CHECK(k == json("hello world"));
+            }
+        }
+
+        SECTION("array_t")
+        {
+            SECTION("array_t type")
+            {
+                json j = {1, 2, 3, 4};
+                json::array_t a = {"foo", "bar", "baz"};
+
+                j.swap(a);
+
+                CHECK(j == json({"foo", "bar", "baz"}));
+
+                j.swap(a);
+
+                CHECK(j == json({1, 2, 3, 4}));
+            }
+
+            SECTION("non-array_t type")
+            {
+                json j = 17;
+                json::array_t a = {"foo", "bar", "baz"};
+
+                CHECK_THROWS_AS(j.swap(a), std::domain_error);
+                CHECK_THROWS_WITH(j.swap(a), "cannot use swap() with number");
+            }
+        }
+
+        SECTION("object_t")
+        {
+            SECTION("object_t type")
+            {
+                json j = {{"one", 1}, {"two", 2}};
+                json::object_t o = {{"cow", "Kuh"}, {"chicken", "Huhn"}};
+
+                j.swap(o);
+
+                CHECK(j == json({{"cow", "Kuh"}, {"chicken", "Huhn"}}));
+
+                j.swap(o);
+
+                CHECK(j == json({{"one", 1}, {"two", 2}}));
+            }
+
+            SECTION("non-object_t type")
+            {
+                json j = 17;
+                json::object_t o = {{"cow", "Kuh"}, {"chicken", "Huhn"}};
+
+                CHECK_THROWS_AS(j.swap(o), std::domain_error);
+                CHECK_THROWS_WITH(j.swap(o), "cannot use swap() with number");
+            }
+        }
+
+        SECTION("string_t")
+        {
+            SECTION("string_t type")
+            {
+                json j = "Hello world";
+                json::string_t s = "Hallo Welt";
+
+                j.swap(s);
+
+                CHECK(j == json("Hallo Welt"));
+
+                j.swap(s);
+
+                CHECK(j == json("Hello world"));
+            }
+
+            SECTION("non-string_t type")
+            {
+                json j = 17;
+                json::string_t s = "Hallo Welt";
+
+                CHECK_THROWS_AS(j.swap(s), std::domain_error);
+                CHECK_THROWS_WITH(j.swap(s), "cannot use swap() with number");
+            }
+        }
+    }
+}

test/src/unit-pointer_access.cpp

@@ -0,0 +1,443 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("pointer access")
+{
+    // create a JSON value with different types
+    json json_types =
+    {
+        {"boolean", true},
+        {
+            "number", {
+                {"integer", 42},
+                {"unsigned", 42u},
+                {"floating-point", 17.23}
+            }
+        },
+        {"string", "Hello, world!"},
+        {"array", {1, 2, 3, 4, 5}},
+        {"null", nullptr}
+    };
+
+    SECTION("pointer access to object_t")
+    {
+        using test_type = json::object_t;
+        json value = {{"one", 1}, {"two", 2}};
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() != nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const object_t")
+    {
+        using test_type = const json::object_t;
+        const json value = {{"one", 1}, {"two", 2}};
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to array_t")
+    {
+        using test_type = json::array_t;
+        json value = {1, 2, 3, 4};
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() != nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const array_t")
+    {
+        using test_type = const json::array_t;
+        const json value = {1, 2, 3, 4};
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to string_t")
+    {
+        using test_type = json::string_t;
+        json value = "hello";
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() != nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const string_t")
+    {
+        using test_type = const json::string_t;
+        const json value = "hello";
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to boolean_t")
+    {
+        using test_type = json::boolean_t;
+        json value = false;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() != nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const boolean_t")
+    {
+        using test_type = const json::boolean_t;
+        const json value = false;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        //CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        //CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        //CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to number_integer_t")
+    {
+        using test_type = json::number_integer_t;
+        json value = 23;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() != nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const number_integer_t")
+    {
+        using test_type = const json::number_integer_t;
+        const json value = 23;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to number_unsigned_t")
+    {
+        using test_type = json::number_unsigned_t;
+        json value = 23u;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() != nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() != nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to const number_unsigned_t")
+    {
+        using test_type = const json::number_unsigned_t;
+        const json value = 23u;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == value.get<test_type>());
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == value.get<test_type>());
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == value.get<test_type>());
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() != nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() == nullptr);
+    }
+
+    SECTION("pointer access to number_float_t")
+    {
+        using test_type = json::number_float_t;
+        json value = 42.23;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == Approx(value.get<test_type>()));
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == Approx(value.get<test_type>()));
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == Approx(value.get<test_type>()));
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<json::number_float_t*>() != nullptr);
+    }
+
+    SECTION("pointer access to const number_float_t")
+    {
+        using test_type = const json::number_float_t;
+        const json value = 42.23;
+
+        // check if pointers are returned correctly
+        test_type* p1 = value.get_ptr<test_type*>();
+        CHECK(p1 == value.get_ptr<test_type*>());
+        CHECK(*p1 == Approx(value.get<test_type>()));
+
+        const test_type* p2 = value.get_ptr<const test_type*>();
+        CHECK(p1 == value.get_ptr<const test_type*>());
+        CHECK(*p2 == Approx(value.get<test_type>()));
+
+        const test_type* const p3 = value.get_ptr<const test_type* const>();
+        CHECK(p1 == value.get_ptr<const test_type* const>());
+        CHECK(*p3 == Approx(value.get<test_type>()));
+
+        // check if null pointers are returned correctly
+        CHECK(value.get_ptr<const json::object_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::array_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::string_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::boolean_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_integer_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_unsigned_t*>() == nullptr);
+        CHECK(value.get_ptr<const json::number_float_t*>() != nullptr);
+    }
+}

test/src/unit-readme.cpp

@@ -0,0 +1,299 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+#include <deque>
+#include <forward_list>
+#include <list>
+#include <unordered_map>
+#include <unordered_set>
+
+TEST_CASE("README", "[hide]")
+{
+    {
+        // redirect std::cout for the README file
+        auto old_cout_buffer = std::cout.rdbuf();
+        std::ostringstream new_stream;
+        std::cout.rdbuf(new_stream.rdbuf());
+        {
+            // create an empty structure (null)
+            json j;
+
+            // add a number that is stored as double (note the implicit conversion of j to an object)
+            j["pi"] = 3.141;
+
+            // add a Boolean that is stored as bool
+            j["happy"] = true;
+
+            // add a string that is stored as std::string
+            j["name"] = "Niels";
+
+            // add another null object by passing nullptr
+            j["nothing"] = nullptr;
+
+            // add an object inside the object
+            j["answer"]["everything"] = 42;
+
+            // add an array that is stored as std::vector (using an initializer list)
+            j["list"] = { 1, 0, 2 };
+
+            // add another object (using an initializer list of pairs)
+            j["object"] = { {"currency", "USD"}, {"value", 42.99} };
+
+            // instead, you could also write (which looks very similar to the JSON above)
+            json j2 =
+            {
+                {"pi", 3.141},
+                {"happy", true},
+                {"name", "Niels"},
+                {"nothing", nullptr},
+                {
+                    "answer", {
+                        {"everything", 42}
+                    }
+                },
+                {"list", {1, 0, 2}},
+                {
+                    "object", {
+                        {"currency", "USD"},
+                        {"value", 42.99}
+                    }
+                }
+            };
+        }
+
+        {
+            // ways to express the empty array []
+            json empty_array_implicit = {{}};
+            json empty_array_explicit = json::array();
+
+            // a way to express the empty object {}
+            json empty_object_explicit = json::object();
+
+            // a way to express an _array_ of key/value pairs [["currency", "USD"], ["value", 42.99]]
+            json array_not_object = { json::array({"currency", "USD"}), json::array({"value", 42.99}) };
+        }
+
+        {
+            // create object from string literal
+            json j = "{ \"happy\": true, \"pi\": 3.141 }"_json;
+
+            // or even nicer with a raw string literal
+            auto j2 = R"(
+          {
+            "happy": true,
+            "pi": 3.141
+          }
+        )"_json;
+
+            // or explicitly
+            auto j3 = json::parse("{ \"happy\": true, \"pi\": 3.141 }");
+
+            // explicit conversion to string
+            std::string s = j.dump();    // {\"happy\":true,\"pi\":3.141}
+
+            // serialization with pretty printing
+            // pass in the amount of spaces to indent
+            std::cout << j.dump(4) << std::endl;
+            // {
+            //     "happy": true,
+            //     "pi": 3.141
+            // }
+
+            std::cout << std::setw(2) << j << std::endl;
+        }
+
+        {
+            // create an array using push_back
+            json j;
+            j.push_back("foo");
+            j.push_back(1);
+            j.push_back(true);
+
+            // iterate the array
+            for (json::iterator it = j.begin(); it != j.end(); ++it)
+            {
+                std::cout << *it << '\n';
+            }
+
+            // range-based for
+            for (auto element : j)
+            {
+                std::cout << element << '\n';
+            }
+
+            // getter/setter
+            const std::string tmp = j[0];
+            j[1] = 42;
+            bool foo = j.at(2);
+
+            // other stuff
+            j.size();     // 3 entries
+            j.empty();    // false
+            j.type();     // json::value_t::array
+            j.clear();    // the array is empty again
+
+            // comparison
+            j == "[\"foo\", 1, true]"_json;  // true
+
+            // create an object
+            json o;
+            o["foo"] = 23;
+            o["bar"] = false;
+            o["baz"] = 3.141;
+
+            // find an entry
+            if (o.find("foo") != o.end())
+            {
+                // there is an entry with key "foo"
+            }
+        }
+
+        {
+            std::vector<int> c_vector {1, 2, 3, 4};
+            json j_vec(c_vector);
+            // [1, 2, 3, 4]
+
+            std::deque<float> c_deque {1.2f, 2.3f, 3.4f, 5.6f};
+            json j_deque(c_deque);
+            // [1.2, 2.3, 3.4, 5.6]
+
+            std::list<bool> c_list {true, true, false, true};
+            json j_list(c_list);
+            // [true, true, false, true]
+
+            std::forward_list<int64_t> c_flist {12345678909876, 23456789098765, 34567890987654, 45678909876543};
+            json j_flist(c_flist);
+            // [12345678909876, 23456789098765, 34567890987654, 45678909876543]
+
+            std::array<unsigned long, 4> c_array {{1, 2, 3, 4}};
+            json j_array(c_array);
+            // [1, 2, 3, 4]
+
+            std::set<std::string> c_set {"one", "two", "three", "four", "one"};
+            json j_set(c_set); // only one entry for "one" is used
+            // ["four", "one", "three", "two"]
+
+            std::unordered_set<std::string> c_uset {"one", "two", "three", "four", "one"};
+            json j_uset(c_uset); // only one entry for "one" is used
+            // maybe ["two", "three", "four", "one"]
+
+            std::multiset<std::string> c_mset {"one", "two", "one", "four"};
+            json j_mset(c_mset); // only one entry for "one" is used
+            // maybe ["one", "two", "four"]
+
+            std::unordered_multiset<std::string> c_umset {"one", "two", "one", "four"};
+            json j_umset(c_umset); // both entries for "one" are used
+            // maybe ["one", "two", "one", "four"]
+        }
+
+        {
+            std::map<std::string, int> c_map { {"one", 1}, {"two", 2}, {"three", 3} };
+            json j_map(c_map);
+            // {"one": 1, "two": 2, "three": 3}
+
+            std::unordered_map<const char*, float> c_umap { {"one", 1.2f}, {"two", 2.3f}, {"three", 3.4f} };
+            json j_umap(c_umap);
+            // {"one": 1.2, "two": 2.3, "three": 3.4}
+
+            std::multimap<std::string, bool> c_mmap { {"one", true}, {"two", true}, {"three", false}, {"three", true} };
+            json j_mmap(c_mmap); // only one entry for key "three" is used
+            // maybe {"one": true, "two": true, "three": true}
+
+            std::unordered_multimap<std::string, bool> c_ummap { {"one", true}, {"two", true}, {"three", false}, {"three", true} };
+            json j_ummap(c_ummap); // only one entry for key "three" is used
+            // maybe {"one": true, "two": true, "three": true}
+        }
+
+        {
+            // strings
+            std::string s1 = "Hello, world!";
+            json js = s1;
+            std::string s2 = js;
+
+            // Booleans
+            bool b1 = true;
+            json jb = b1;
+            bool b2 = jb;
+
+            // numbers
+            int i = 42;
+            json jn = i;
+            double f = jn;
+
+            // etc.
+
+            std::string vs = js.get<std::string>();
+            bool vb = jb.get<bool>();
+            int vi = jn.get<int>();
+
+            // etc.
+        }
+
+        {
+            // a JSON value
+            json j_original = R"({
+          "baz": ["one", "two", "three"],
+          "foo": "bar"
+        })"_json;
+
+            // access members with a JSON pointer (RFC 6901)
+            j_original["/baz/1"_json_pointer];
+            // "two"
+
+            // a JSON patch (RFC 6902)
+            json j_patch = R"([
+          { "op": "replace", "path": "/baz", "value": "boo" },
+          { "op": "add", "path": "/hello", "value": ["world"] },
+          { "op": "remove", "path": "/foo"}
+        ])"_json;
+
+            // apply the patch
+            json j_result = j_original.patch(j_patch);
+            // {
+            //    "baz": "boo",
+            //    "hello": ["world"]
+            // }
+
+            // calculate a JSON patch from two JSON values
+            json::diff(j_result, j_original);
+            // [
+            //   { "op":" replace", "path": "/baz", "value": ["one", "two", "three"] },
+            //   { "op":"remove","path":"/hello" },
+            //   { "op":"add","path":"/foo","value":"bar" }
+            // ]
+        }
+
+        // restore old std::cout
+        std::cout.rdbuf(old_cout_buffer);
+    }
+}

test/src/unit-reference_access.cpp

@@ -0,0 +1,202 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("reference access")
+{
+    // create a JSON value with different types
+    json json_types =
+    {
+        {"boolean", true},
+        {
+            "number", {
+                {"integer", 42},
+                {"floating-point", 17.23}
+            }
+        },
+        {"string", "Hello, world!"},
+        {"array", {1, 2, 3, 4, 5}},
+        {"null", nullptr}
+    };
+
+    SECTION("reference access to object_t")
+    {
+        using test_type = json::object_t;
+        json value = {{"one", 1}, {"two", 2}};
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_NOTHROW(value.get_ref<json::object_t&>());
+        CHECK_THROWS(value.get_ref<json::array_t&>());
+        CHECK_THROWS(value.get_ref<json::string_t&>());
+        CHECK_THROWS(value.get_ref<json::boolean_t&>());
+        CHECK_THROWS(value.get_ref<json::number_integer_t&>());
+        CHECK_THROWS(value.get_ref<json::number_float_t&>());
+    }
+
+    SECTION("const reference access to const object_t")
+    {
+        using test_type = json::object_t;
+        const json value = {{"one", 1}, {"two", 2}};
+
+        // this should not compile
+        // test_type& p1 = value.get_ref<test_type&>();
+
+        // check if references are returned correctly
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+    }
+
+    SECTION("reference access to array_t")
+    {
+        using test_type = json::array_t;
+        json value = {1, 2, 3, 4};
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_THROWS(value.get_ref<json::object_t&>());
+        CHECK_NOTHROW(value.get_ref<json::array_t&>());
+        CHECK_THROWS(value.get_ref<json::string_t&>());
+        CHECK_THROWS(value.get_ref<json::boolean_t&>());
+        CHECK_THROWS(value.get_ref<json::number_integer_t&>());
+        CHECK_THROWS(value.get_ref<json::number_float_t&>());
+    }
+
+    SECTION("reference access to string_t")
+    {
+        using test_type = json::string_t;
+        json value = "hello";
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_THROWS(value.get_ref<json::object_t&>());
+        CHECK_THROWS(value.get_ref<json::array_t&>());
+        CHECK_NOTHROW(value.get_ref<json::string_t&>());
+        CHECK_THROWS(value.get_ref<json::boolean_t&>());
+        CHECK_THROWS(value.get_ref<json::number_integer_t&>());
+        CHECK_THROWS(value.get_ref<json::number_float_t&>());
+    }
+
+    SECTION("reference access to boolean_t")
+    {
+        using test_type = json::boolean_t;
+        json value = false;
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_THROWS(value.get_ref<json::object_t&>());
+        CHECK_THROWS(value.get_ref<json::array_t&>());
+        CHECK_THROWS(value.get_ref<json::string_t&>());
+        CHECK_NOTHROW(value.get_ref<json::boolean_t&>());
+        CHECK_THROWS(value.get_ref<json::number_integer_t&>());
+        CHECK_THROWS(value.get_ref<json::number_float_t&>());
+    }
+
+    SECTION("reference access to number_integer_t")
+    {
+        using test_type = json::number_integer_t;
+        json value = 23;
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_THROWS(value.get_ref<json::object_t&>());
+        CHECK_THROWS(value.get_ref<json::array_t&>());
+        CHECK_THROWS(value.get_ref<json::string_t&>());
+        CHECK_THROWS(value.get_ref<json::boolean_t&>());
+        CHECK_NOTHROW(value.get_ref<json::number_integer_t&>());
+        CHECK_THROWS(value.get_ref<json::number_float_t&>());
+    }
+
+    SECTION("reference access to number_float_t")
+    {
+        using test_type = json::number_float_t;
+        json value = 42.23;
+
+        // check if references are returned correctly
+        test_type& p1 = value.get_ref<test_type&>();
+        CHECK(&p1 == value.get_ptr<test_type*>());
+        CHECK(p1 == value.get<test_type>());
+
+        const test_type& p2 = value.get_ref<const test_type&>();
+        CHECK(&p2 == value.get_ptr<const test_type*>());
+        CHECK(p2 == value.get<test_type>());
+
+        // check if mismatching references throw correctly
+        CHECK_THROWS(value.get_ref<json::object_t&>());
+        CHECK_THROWS(value.get_ref<json::array_t&>());
+        CHECK_THROWS(value.get_ref<json::string_t&>());
+        CHECK_THROWS(value.get_ref<json::boolean_t&>());
+        CHECK_THROWS(value.get_ref<json::number_integer_t&>());
+        CHECK_NOTHROW(value.get_ref<json::number_float_t&>());
+    }
+}

test/src/unit-regression.cpp

@@ -0,0 +1,443 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("regression tests")
+{
+    SECTION("issue #60 - Double quotation mark is not parsed correctly")
+    {
+        SECTION("escape_dobulequote")
+        {
+            auto s = "[\"\\\"foo\\\"\"]";
+            json j = json::parse(s);
+            auto expected = R"(["\"foo\""])"_json;
+            CHECK(j == expected);
+        }
+    }
+
+    SECTION("issue #70 - Handle infinity and NaN cases")
+    {
+        SECTION("NAN value")
+        {
+            CHECK(json(NAN) == json());
+            CHECK(json(json::number_float_t(NAN)) == json());
+        }
+
+        SECTION("infinity")
+        {
+            CHECK(json(INFINITY) == json());
+            CHECK(json(json::number_float_t(INFINITY)) == json());
+        }
+    }
+
+    SECTION("pull request #71 - handle enum type")
+    {
+        enum { t = 0 };
+        json j = json::array();
+        j.push_back(t);
+
+        j.push_back(json::object(
+        {
+            {"game_type", t}
+        }));
+    }
+
+    SECTION("issue #76 - dump() / parse() not idempotent")
+    {
+        // create JSON object
+        json fields;
+        fields["one"] = std::string("one");
+        fields["two"] = std::string("two three");
+        fields["three"] = std::string("three \"four\"");
+
+        // create another JSON object by deserializing the serialization
+        std::string payload = fields.dump();
+        json parsed_fields = json::parse(payload);
+
+        // check individual fields to match both objects
+        CHECK(parsed_fields["one"] == fields["one"]);
+        CHECK(parsed_fields["two"] == fields["two"]);
+        CHECK(parsed_fields["three"] == fields["three"]);
+
+        // check individual fields to match original input
+        CHECK(parsed_fields["one"] == std::string("one"));
+        CHECK(parsed_fields["two"] == std::string("two three"));
+        CHECK(parsed_fields["three"] == std::string("three \"four\""));
+
+        // check equality of the objects
+        CHECK(parsed_fields == fields);
+
+        // check equality of the serialized objects
+        CHECK(fields.dump() == parsed_fields.dump());
+
+        // check everything in one line
+        CHECK(fields == json::parse(fields.dump()));
+    }
+
+    SECTION("issue #82 - lexer::get_number return NAN")
+    {
+        const auto content = R"(
+        {
+            "Test":"Test1",
+            "Number":100,
+            "Foo":42.42
+        })";
+
+        std::stringstream ss;
+        ss << content;
+        json j;
+        ss >> j;
+
+        std::string test = j["Test"];
+        CHECK(test == "Test1");
+        int number = j["Number"];
+        CHECK(number == 100);
+        float foo = j["Foo"];
+        CHECK(foo == Approx(42.42));
+    }
+
+    SECTION("issue #89 - nonstandard integer type")
+    {
+        // create JSON class with nonstandard integer number type
+        using custom_json =
+            nlohmann::basic_json<std::map, std::vector, std::string, bool, int32_t, uint32_t, float>;
+        custom_json j;
+        j["int_1"] = 1;
+        // we need to cast to int to compile with Catch - the value is int32_t
+        CHECK(static_cast<int>(j["int_1"]) == 1);
+
+        // tests for correct handling of non-standard integers that overflow the type selected by the user
+
+        // unsigned integer object creation - expected to wrap and still be stored as an integer
+        j = 4294967296U; // 2^32
+        CHECK(static_cast<int>(j.type()) == static_cast<int>(custom_json::value_t::number_unsigned));
+        CHECK(j.get<uint32_t>() == 0);  // Wrap
+
+        // unsigned integer parsing - expected to overflow and be stored as a float
+        j = custom_json::parse("4294967296"); // 2^32
+        CHECK(static_cast<int>(j.type()) == static_cast<int>(custom_json::value_t::number_float));
+        CHECK(j.get<float>() == 4294967296.0f);
+
+        // integer object creation - expected to wrap and still be stored as an integer
+        j = -2147483649LL; // -2^31-1
+        CHECK(static_cast<int>(j.type()) == static_cast<int>(custom_json::value_t::number_integer));
+        CHECK(j.get<int32_t>() == 2147483647);  // Wrap
+
+        // integer parsing - expected to overflow and be stored as a float with rounding
+        j = custom_json::parse("-2147483649"); // -2^31
+        CHECK(static_cast<int>(j.type()) == static_cast<int>(custom_json::value_t::number_float));
+        CHECK(j.get<float>() == -2147483650.0f);
+    }
+
+    SECTION("issue #93 reverse_iterator operator inheritance problem")
+    {
+        {
+            json a = {1, 2, 3};
+            json::reverse_iterator rit = a.rbegin();
+            ++rit;
+            CHECK(*rit == json(2));
+            CHECK(rit.value() == json(2));
+        }
+        {
+            json a = {1, 2, 3};
+            json::reverse_iterator rit = ++a.rbegin();
+        }
+        {
+            json a = {1, 2, 3};
+            json::reverse_iterator rit = a.rbegin();
+            ++rit;
+            json b = {0, 0, 0};
+            std::transform(rit, a.rend(), b.rbegin(), [](json el)
+            {
+                return el;
+            });
+            CHECK(b == json({0, 1, 2}));
+        }
+        {
+            json a = {1, 2, 3};
+            json b = {0, 0, 0};
+            std::transform(++a.rbegin(), a.rend(), b.rbegin(), [](json el)
+            {
+                return el;
+            });
+            CHECK(b == json({0, 1, 2}));
+        }
+    }
+
+    SECTION("issue #100 - failed to iterator json object with reverse_iterator")
+    {
+        json config =
+        {
+            { "111", 111 },
+            { "112", 112 },
+            { "113", 113 }
+        };
+
+        std::stringstream ss;
+
+        for (auto it = config.begin(); it != config.end(); ++it)
+        {
+            ss << it.key() << ": " << it.value() << '\n';
+        }
+
+        for (auto it = config.rbegin(); it != config.rend(); ++it)
+        {
+            ss << it.key() << ": " << it.value() << '\n';
+        }
+
+        CHECK(ss.str() == "111: 111\n112: 112\n113: 113\n113: 113\n112: 112\n111: 111\n");
+    }
+
+    SECTION("issue #101 - binary string causes numbers to be dumped as hex")
+    {
+        int64_t number = 10;
+        std::string bytes{"\x00" "asdf\n", 6};
+        json j;
+        j["int64"] = number;
+        j["binary string"] = bytes;
+        // make sure the number is really printed as decimal "10" and not as
+        // hexadecimal "a"
+        CHECK(j.dump() == "{\"binary string\":\"\\u0000asdf\\n\",\"int64\":10}");
+    }
+
+    SECTION("issue #111 - subsequent unicode chars")
+    {
+        std::string bytes{0x7, 0x7};
+        json j;
+        j["string"] = bytes;
+        CHECK(j["string"] == "\u0007\u0007");
+    }
+
+    SECTION("issue #144 - implicit assignment to std::string fails")
+    {
+        json o = {{"name", "value"}};
+
+        std::string s1 = o["name"];
+        CHECK(s1 == "value");
+
+        std::string s2;
+        s2 = o["name"];
+
+        CHECK(s2 == "value");
+    }
+
+    SECTION("issue #146 - character following a surrogate pair is skipped")
+    {
+        CHECK(json::parse("\"\\ud80c\\udc60abc\"").get<json::string_t>() == u8"\U00013060abc");
+    }
+
+    SECTION("issue #171 - Cannot index by key of type static constexpr const char*")
+    {
+        json j;
+
+        // Non-const access with key as "char []"
+        char array_key[] = "Key1";
+        CHECK_NOTHROW(j[array_key] = 1);
+        CHECK(j[array_key] == json(1));
+
+        // Non-const access with key as "const char[]"
+        const char const_array_key[] = "Key2";
+        CHECK_NOTHROW(j[const_array_key] = 2);
+        CHECK(j[const_array_key] == json(2));
+
+        // Non-const access with key as "char *"
+        char _ptr_key[] = "Key3";
+        char* ptr_key = &_ptr_key[0];
+        CHECK_NOTHROW(j[ptr_key] = 3);
+        CHECK(j[ptr_key] == json(3));
+
+        // Non-const access with key as "const char *"
+        const char* const_ptr_key = "Key4";
+        CHECK_NOTHROW(j[const_ptr_key] = 4);
+        CHECK(j[const_ptr_key] == json(4));
+
+        // Non-const access with key as "static constexpr const char *"
+        static constexpr const char* constexpr_ptr_key = "Key5";
+        CHECK_NOTHROW(j[constexpr_ptr_key] = 5);
+        CHECK(j[constexpr_ptr_key] == json(5));
+
+        const json j_const = j;
+
+        // Const access with key as "char []"
+        CHECK(j_const[array_key] == json(1));
+
+        // Const access with key as "const char[]"
+        CHECK(j_const[const_array_key] == json(2));
+
+        // Const access with key as "char *"
+        CHECK(j_const[ptr_key] == json(3));
+
+        // Const access with key as "const char *"
+        CHECK(j_const[const_ptr_key] == json(4));
+
+        // Const access with key as "static constexpr const char *"
+        CHECK(j_const[constexpr_ptr_key] == json(5));
+    }
+
+    SECTION("issue #186 miloyip/nativejson-benchmark: floating-point parsing")
+    {
+        json j;
+
+        j = json::parse("-0.0");
+        CHECK(j.get<double>() == -0.0);
+
+        j = json::parse("2.22507385850720113605740979670913197593481954635164564e-308");
+        CHECK(j.get<double>() == 2.2250738585072009e-308);
+
+        j = json::parse("0.999999999999999944488848768742172978818416595458984374");
+        CHECK(j.get<double>() == 0.99999999999999989);
+
+        j = json::parse("1.00000000000000011102230246251565404236316680908203126");
+        CHECK(j.get<double>() == 1.00000000000000022);
+
+        j = json::parse("7205759403792793199999e-5");
+        CHECK(j.get<double>() == 72057594037927928.0);
+
+        j = json::parse("922337203685477529599999e-5");
+        CHECK(j.get<double>() == 9223372036854774784.0);
+
+        j = json::parse("1014120480182583464902367222169599999e-5");
+        CHECK(j.get<double>() == 10141204801825834086073718800384.0);
+
+        j = json::parse("5708990770823839207320493820740630171355185151999e-3");
+        CHECK(j.get<double>() == 5708990770823838890407843763683279797179383808.0);
+
+        // create JSON class with nonstandard float number type
+
+        // float
+        nlohmann::basic_json<std::map, std::vector, std::string, bool, int32_t, uint32_t, float> j_float =
+            1.23e25f;
+        CHECK(j_float.get<float>() == 1.23e25f);
+
+        // double
+        nlohmann::basic_json<std::map, std::vector, std::string, bool, int64_t, uint64_t, double> j_double =
+            1.23e35f;
+        CHECK(j_double.get<double>() == 1.23e35f);
+
+        // long double
+        nlohmann::basic_json<std::map, std::vector, std::string, bool, int64_t, uint64_t, long double>
+        j_long_double = 1.23e45L;
+        CHECK(j_long_double.get<long double>() == 1.23e45L);
+    }
+
+    SECTION("issue #228 - double values are serialized with commas as decimal points")
+    {
+        json j1a = 23.42;
+        json j1b = json::parse("23.42");
+
+        json j2a = 2342e-2;
+        //issue #230
+        //json j2b = json::parse("2342e-2");
+
+        json j3a = 10E3;
+        json j3b = json::parse("10E3");
+        json j3c = json::parse("10e3");
+
+        // class to create a locale that would use a comma for decimals
+        class CommaDecimalSeparator : public std::numpunct<char>
+        {
+          protected:
+            char do_decimal_point() const
+            {
+                return ',';
+            }
+        };
+
+        // change locale to mess with decimal points
+        std::locale::global(std::locale(std::locale(), new CommaDecimalSeparator));
+
+        CHECK(j1a.dump() == "23.42");
+        CHECK(j1b.dump() == "23.42");
+
+        // check if locale is properly reset
+        std::stringstream ss;
+        ss.imbue(std::locale(std::locale(), new CommaDecimalSeparator));
+        ss << 47.11;
+        CHECK(ss.str() == "47,11");
+        ss << j1a;
+        CHECK(ss.str() == "47,1123.42");
+        ss << 47.11;
+        CHECK(ss.str() == "47,1123.4247,11");
+
+        CHECK(j2a.dump() == "23.42");
+        //issue #230
+        //CHECK(j2b.dump() == "23.42");
+
+        CHECK(j3a.dump() == "10000");
+        CHECK(j3b.dump() == "10000");
+        CHECK(j3c.dump() == "10000");
+        //CHECK(j3b.dump() == "1E04"); // roundtrip error
+        //CHECK(j3c.dump() == "1e04"); // roundtrip error
+    }
+
+    SECTION("issue #233 - Can't use basic_json::iterator as a base iterator for std::move_iterator")
+    {
+        json source = {"a", "b", "c"};
+        json expected = {"a", "b"};
+        json dest;
+
+        std::copy_n(std::make_move_iterator(source.begin()), 2, std::back_inserter(dest));
+
+        CHECK(dest == expected);
+    }
+
+    SECTION("issue #235 - ambiguous overload for 'push_back' and 'operator+='")
+    {
+        json data = {{"key", "value"}};
+        data.push_back({"key2", "value2"});
+        data += {"key3", "value3"};
+
+        CHECK(data == json({{"key", "value"}, {"key2", "value2"}, {"key3", "value3"}}));
+    }
+
+    SECTION("issue #269 - diff generates incorrect patch when removing multiple array elements")
+    {
+        json doc = R"( { "arr1": [1, 2, 3, 4] } )"_json;
+        json expected = R"( { "arr1": [1, 2] } )"_json;
+
+        // check roundtrip
+        CHECK(doc.patch(json::diff(doc, expected)) == expected);
+    }
+
+    SECTION("issue #283 - value() does not work with _json_pointer types")
+    {
+        json j =
+        {
+            {"object", {{"key1", 1}, {"key2", 2}}},
+        };
+
+        int at_integer = j.at("/object/key2"_json_pointer);
+        int val_integer = j.value("/object/key2"_json_pointer, 0);
+
+        CHECK(at_integer == val_integer);
+    }
+}

test/src/unit-serialization.cpp

@@ -0,0 +1,76 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+TEST_CASE("serialization")
+{
+    SECTION("operator<<")
+    {
+        SECTION("no given width")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            ss << j;
+            CHECK(ss.str() == "[\"foo\",1,2,3,false,{\"one\":1}]");
+        }
+
+        SECTION("given width")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            ss << std::setw(4) << j;
+            CHECK(ss.str() ==
+                  "[\n    \"foo\",\n    1,\n    2,\n    3,\n    false,\n    {\n        \"one\": 1\n    }\n]");
+        }
+    }
+
+    SECTION("operator>>")
+    {
+        SECTION("no given width")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            j >> ss;
+            CHECK(ss.str() == "[\"foo\",1,2,3,false,{\"one\":1}]");
+        }
+
+        SECTION("given width")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            ss.width(4);
+            j >> ss;
+            CHECK(ss.str() ==
+                  "[\n    \"foo\",\n    1,\n    2,\n    3,\n    false,\n    {\n        \"one\": 1\n    }\n]");
+        }
+    }
+}

test/src/unit-testsuites.cpp

@@ -0,0 +1,436 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#include "json.hpp"
+using nlohmann::json;
+
+#include <fstream>
+
+TEST_CASE("compliance tests from json.org")
+{
+    // test cases are from http://json.org/JSON_checker/
+
+    SECTION("expected failures")
+    {
+        for (auto filename :
+                {
+                    //"test/data/json_tests/fail1.json",
+                    "test/data/json_tests/fail2.json",
+                    "test/data/json_tests/fail3.json",
+                    "test/data/json_tests/fail4.json",
+                    "test/data/json_tests/fail5.json",
+                    "test/data/json_tests/fail6.json",
+                    "test/data/json_tests/fail7.json",
+                    "test/data/json_tests/fail8.json",
+                    "test/data/json_tests/fail9.json",
+                    "test/data/json_tests/fail10.json",
+                    "test/data/json_tests/fail11.json",
+                    "test/data/json_tests/fail12.json",
+                    "test/data/json_tests/fail13.json",
+                    "test/data/json_tests/fail14.json",
+                    "test/data/json_tests/fail15.json",
+                    "test/data/json_tests/fail16.json",
+                    "test/data/json_tests/fail17.json",
+                    //"test/data/json_tests/fail18.json",
+                    "test/data/json_tests/fail19.json",
+                    "test/data/json_tests/fail20.json",
+                    "test/data/json_tests/fail21.json",
+                    "test/data/json_tests/fail22.json",
+                    "test/data/json_tests/fail23.json",
+                    "test/data/json_tests/fail24.json",
+                    "test/data/json_tests/fail25.json",
+                    "test/data/json_tests/fail26.json",
+                    "test/data/json_tests/fail27.json",
+                    "test/data/json_tests/fail28.json",
+                    "test/data/json_tests/fail29.json",
+                    "test/data/json_tests/fail30.json",
+                    "test/data/json_tests/fail31.json",
+                    "test/data/json_tests/fail32.json",
+                    "test/data/json_tests/fail33.json"
+                })
+        {
+            CAPTURE(filename);
+            json j;
+            std::ifstream f(filename);
+            CHECK_THROWS_AS(j << f, std::invalid_argument);
+        }
+    }
+
+    SECTION("expected passes")
+    {
+        for (auto filename :
+                {
+                    "test/data/json_tests/pass1.json",
+                    "test/data/json_tests/pass2.json",
+                    "test/data/json_tests/pass3.json"
+                })
+        {
+            CAPTURE(filename);
+            json j;
+            std::ifstream f(filename);
+            CHECK_NOTHROW(j << f);
+        }
+    }
+}
+
+TEST_CASE("compliance tests from nativejson-benchmark")
+{
+    // test cases from https://github.com/miloyip/nativejson-benchmark/blob/master/src/main.cpp
+
+    SECTION("doubles")
+    {
+        auto TEST_DOUBLE = [](const std::string & json_string, const double expected)
+        {
+            CAPTURE(json_string);
+            CAPTURE(expected);
+            CHECK(json::parse(json_string)[0].get<double>() == Approx(expected));
+        };
+
+        TEST_DOUBLE("[0.0]", 0.0);
+        TEST_DOUBLE("[-0.0]", -0.0);
+        TEST_DOUBLE("[1.0]", 1.0);
+        TEST_DOUBLE("[-1.0]", -1.0);
+        TEST_DOUBLE("[1.5]", 1.5);
+        TEST_DOUBLE("[-1.5]", -1.5);
+        TEST_DOUBLE("[3.1416]", 3.1416);
+        TEST_DOUBLE("[1E10]", 1E10);
+        TEST_DOUBLE("[1e10]", 1e10);
+        TEST_DOUBLE("[1E+10]", 1E+10);
+        TEST_DOUBLE("[1E-10]", 1E-10);
+        TEST_DOUBLE("[-1E10]", -1E10);
+        TEST_DOUBLE("[-1e10]", -1e10);
+        TEST_DOUBLE("[-1E+10]", -1E+10);
+        TEST_DOUBLE("[-1E-10]", -1E-10);
+        TEST_DOUBLE("[1.234E+10]", 1.234E+10);
+        TEST_DOUBLE("[1.234E-10]", 1.234E-10);
+        TEST_DOUBLE("[1.79769e+308]", 1.79769e+308);
+        TEST_DOUBLE("[2.22507e-308]", 2.22507e-308);
+        TEST_DOUBLE("[-1.79769e+308]", -1.79769e+308);
+        TEST_DOUBLE("[-2.22507e-308]", -2.22507e-308);
+        TEST_DOUBLE("[4.9406564584124654e-324]", 4.9406564584124654e-324); // minimum denormal
+        TEST_DOUBLE("[2.2250738585072009e-308]", 2.2250738585072009e-308); // Max subnormal double
+        TEST_DOUBLE("[2.2250738585072014e-308]", 2.2250738585072014e-308); // Min normal positive double
+        TEST_DOUBLE("[1.7976931348623157e+308]", 1.7976931348623157e+308); // Max double
+        TEST_DOUBLE("[1e-10000]", 0.0);                                   // must underflow
+        TEST_DOUBLE("[18446744073709551616]",
+                    18446744073709551616.0);    // 2^64 (max of uint64_t + 1, force to use double)
+        TEST_DOUBLE("[-9223372036854775809]",
+                    -9223372036854775809.0);    // -2^63 - 1(min of int64_t + 1, force to use double)
+        TEST_DOUBLE("[0.9868011474609375]",
+                    0.9868011474609375);          // https://github.com/miloyip/rapidjson/issues/120
+        TEST_DOUBLE("[123e34]", 123e34);                                  // Fast Path Cases In Disguise
+        TEST_DOUBLE("[45913141877270640000.0]", 45913141877270640000.0);
+        TEST_DOUBLE("[2.2250738585072011e-308]",
+                    2.2250738585072011e-308);
+        //TEST_DOUBLE("[1e-00011111111111]", 0.0);
+        //TEST_DOUBLE("[-1e-00011111111111]", -0.0);
+        TEST_DOUBLE("[1e-214748363]", 0.0);
+        TEST_DOUBLE("[1e-214748364]", 0.0);
+        //TEST_DOUBLE("[1e-21474836311]", 0.0);
+        TEST_DOUBLE("[0.017976931348623157e+310]", 1.7976931348623157e+308); // Max double in another form
+
+        // Since
+        // abs((2^-1022 - 2^-1074) - 2.2250738585072012e-308) = 3.109754131239141401123495768877590405345064751974375599... ¡Á 10^-324
+        // abs((2^-1022) - 2.2250738585072012e-308) = 1.830902327173324040642192159804623318305533274168872044... ¡Á 10 ^ -324
+        // So 2.2250738585072012e-308 should round to 2^-1022 = 2.2250738585072014e-308
+        TEST_DOUBLE("[2.2250738585072012e-308]",
+                    2.2250738585072014e-308);
+
+        // More closer to normal/subnormal boundary
+        // boundary = 2^-1022 - 2^-1075 = 2.225073858507201136057409796709131975934819546351645648... ¡Á 10^-308
+        TEST_DOUBLE("[2.22507385850720113605740979670913197593481954635164564e-308]",
+                    2.2250738585072009e-308);
+        TEST_DOUBLE("[2.22507385850720113605740979670913197593481954635164565e-308]",
+                    2.2250738585072014e-308);
+
+        // 1.0 is in (1.0 - 2^-54, 1.0 + 2^-53)
+        // 1.0 - 2^-54 = 0.999999999999999944488848768742172978818416595458984375
+        TEST_DOUBLE("[0.999999999999999944488848768742172978818416595458984375]", 1.0); // round to even
+        TEST_DOUBLE("[0.999999999999999944488848768742172978818416595458984374]",
+                    0.99999999999999989); // previous double
+        TEST_DOUBLE("[0.999999999999999944488848768742172978818416595458984376]", 1.0); // next double
+        // 1.0 + 2^-53 = 1.00000000000000011102230246251565404236316680908203125
+        TEST_DOUBLE("[1.00000000000000011102230246251565404236316680908203125]", 1.0); // round to even
+        TEST_DOUBLE("[1.00000000000000011102230246251565404236316680908203124]", 1.0); // previous double
+        TEST_DOUBLE("[1.00000000000000011102230246251565404236316680908203126]",
+                    1.00000000000000022); // next double
+
+        // Numbers from https://github.com/floitsch/double-conversion/blob/master/test/cctest/test-strtod.cc
+
+        TEST_DOUBLE("[72057594037927928.0]", 72057594037927928.0);
+        TEST_DOUBLE("[72057594037927936.0]", 72057594037927936.0);
+        TEST_DOUBLE("[72057594037927932.0]", 72057594037927936.0);
+        TEST_DOUBLE("[7205759403792793199999e-5]", 72057594037927928.0);
+        TEST_DOUBLE("[7205759403792793200001e-5]", 72057594037927936.0);
+
+        TEST_DOUBLE("[9223372036854774784.0]", 9223372036854774784.0);
+        TEST_DOUBLE("[9223372036854775808.0]", 9223372036854775808.0);
+        TEST_DOUBLE("[9223372036854775296.0]", 9223372036854775808.0);
+        TEST_DOUBLE("[922337203685477529599999e-5]", 9223372036854774784.0);
+        TEST_DOUBLE("[922337203685477529600001e-5]", 9223372036854775808.0);
+
+        TEST_DOUBLE("[10141204801825834086073718800384]", 10141204801825834086073718800384.0);
+        TEST_DOUBLE("[10141204801825835211973625643008]", 10141204801825835211973625643008.0);
+        TEST_DOUBLE("[10141204801825834649023672221696]", 10141204801825835211973625643008.0);
+        TEST_DOUBLE("[1014120480182583464902367222169599999e-5]", 10141204801825834086073718800384.0);
+        TEST_DOUBLE("[1014120480182583464902367222169600001e-5]", 10141204801825835211973625643008.0);
+
+        TEST_DOUBLE("[5708990770823838890407843763683279797179383808]",
+                    5708990770823838890407843763683279797179383808.0);
+        TEST_DOUBLE("[5708990770823839524233143877797980545530986496]",
+                    5708990770823839524233143877797980545530986496.0);
+        TEST_DOUBLE("[5708990770823839207320493820740630171355185152]",
+                    5708990770823839524233143877797980545530986496.0);
+        TEST_DOUBLE("[5708990770823839207320493820740630171355185151999e-3]",
+                    5708990770823838890407843763683279797179383808.0);
+        TEST_DOUBLE("[5708990770823839207320493820740630171355185152001e-3]",
+                    5708990770823839524233143877797980545530986496.0);
+
+        {
+            char n1e308[312];   // '1' followed by 308 '0'
+            n1e308[0] = '[';
+            n1e308[1] = '1';
+            for (int j = 2; j < 310; j++)
+            {
+                n1e308[j] = '0';
+            }
+            n1e308[310] = ']';
+            n1e308[311] = '\0';
+            TEST_DOUBLE(n1e308, 1E308);
+        }
+
+        // Cover trimming
+        TEST_DOUBLE(
+            "[2.22507385850720113605740979670913197593481954635164564802342610972482222202107694551652952390813508"
+            "7914149158913039621106870086438694594645527657207407820621743379988141063267329253552286881372149012"
+            "9811224514518898490572223072852551331557550159143974763979834118019993239625482890171070818506906306"
+            "6665599493827577257201576306269066333264756530000924588831643303777979186961204949739037782970490505"
+            "1080609940730262937128958950003583799967207254304360284078895771796150945516748243471030702609144621"
+            "5722898802581825451803257070188608721131280795122334262883686223215037756666225039825343359745688844"
+            "2390026549819838548794829220689472168983109969836584681402285424333066033985088644580400103493397042"
+            "7567186443383770486037861622771738545623065874679014086723327636718751234567890123456789012345678901"
+            "e-308]",
+            2.2250738585072014e-308);
+    }
+
+    SECTION("strings")
+    {
+        auto TEST_STRING = [](const std::string & json_string, const std::string & expected)
+        {
+            CAPTURE(json_string);
+            CAPTURE(expected);
+            CHECK(json::parse(json_string)[0].get<std::string>() == expected);
+        };
+
+        TEST_STRING("[\"\"]", "");
+        TEST_STRING("[\"Hello\"]", "Hello");
+        TEST_STRING("[\"Hello\\nWorld\"]", "Hello\nWorld");
+        //TEST_STRING("[\"Hello\\u0000World\"]", "Hello\0World");
+        TEST_STRING("[\"\\\"\\\\/\\b\\f\\n\\r\\t\"]", "\"\\/\b\f\n\r\t");
+        TEST_STRING("[\"\\u0024\"]", "\x24");         // Dollar sign U+0024
+        TEST_STRING("[\"\\u00A2\"]", "\xC2\xA2");     // Cents sign U+00A2
+        TEST_STRING("[\"\\u20AC\"]", "\xE2\x82\xAC"); // Euro sign U+20AC
+        TEST_STRING("[\"\\uD834\\uDD1E\"]", "\xF0\x9D\x84\x9E");  // G clef sign U+1D11E
+    }
+
+    SECTION("roundtrip")
+    {
+        // test cases are from https://github.com/miloyip/nativejson-benchmark/tree/master/test/data/roundtrip
+
+        for (auto filename :
+                {
+                    "test/data/json_roundtrip/roundtrip01.json",
+                    "test/data/json_roundtrip/roundtrip02.json",
+                    "test/data/json_roundtrip/roundtrip03.json",
+                    "test/data/json_roundtrip/roundtrip04.json",
+                    "test/data/json_roundtrip/roundtrip05.json",
+                    "test/data/json_roundtrip/roundtrip06.json",
+                    "test/data/json_roundtrip/roundtrip07.json",
+                    "test/data/json_roundtrip/roundtrip08.json",
+                    "test/data/json_roundtrip/roundtrip09.json",
+                    "test/data/json_roundtrip/roundtrip10.json",
+                    "test/data/json_roundtrip/roundtrip11.json",
+                    "test/data/json_roundtrip/roundtrip12.json",
+                    "test/data/json_roundtrip/roundtrip13.json",
+                    "test/data/json_roundtrip/roundtrip14.json",
+                    "test/data/json_roundtrip/roundtrip15.json",
+                    "test/data/json_roundtrip/roundtrip16.json",
+                    "test/data/json_roundtrip/roundtrip17.json",
+                    "test/data/json_roundtrip/roundtrip18.json",
+                    "test/data/json_roundtrip/roundtrip19.json",
+                    "test/data/json_roundtrip/roundtrip20.json",
+                    "test/data/json_roundtrip/roundtrip21.json",
+                    "test/data/json_roundtrip/roundtrip22.json",
+                    "test/data/json_roundtrip/roundtrip23.json",
+                    //"test/data/json_roundtrip/roundtrip24.json", // roundtrip error
+                    //"test/data/json_roundtrip/roundtrip25.json", // roundtrip error
+                    //"test/data/json_roundtrip/roundtrip26.json", // roundtrip error
+                    //"test/data/json_roundtrip/roundtrip27.json", // roundtrip error
+                    //"test/data/json_roundtrip/roundtrip28.json", // roundtrip error
+                    "test/data/json_roundtrip/roundtrip29.json",
+                    //"test/data/json_roundtrip/roundtrip30.json", // roundtrip error
+                    //"test/data/json_roundtrip/roundtrip31.json", // roundtrip error
+                    "test/data/json_roundtrip/roundtrip32.json"
+                })
+        {
+            CAPTURE(filename);
+            std::ifstream f(filename);
+            std::string json_string( (std::istreambuf_iterator<char>(f) ),
+                                     (std::istreambuf_iterator<char>()) );
+
+            json j = json::parse(json_string);
+            CHECK(j.dump() == json_string);
+        }
+    }
+}
+
+TEST_CASE("test suite from json-test-suite")
+{
+    SECTION("read all sample.json")
+    {
+        // read a file with all unicode characters stored as single-character
+        // strings in a JSON array
+        std::ifstream f("test/data/json_testsuite/sample.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+
+        // the array has 3 elements
+        CHECK(j.size() == 3);
+    }
+}
+
+TEST_CASE("json.org examples")
+{
+    // here, we list all JSON values from http://json.org/example
+
+    SECTION("1.json")
+    {
+        std::ifstream f("test/data/json.org/1.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+
+    SECTION("2.json")
+    {
+        std::ifstream f("test/data/json.org/2.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+
+    SECTION("3.json")
+    {
+        std::ifstream f("test/data/json.org/3.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+
+    SECTION("4.json")
+    {
+        std::ifstream f("test/data/json.org/4.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+
+    SECTION("5.json")
+    {
+        std::ifstream f("test/data/json.org/5.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+}
+
+TEST_CASE("RFC 7159 examples")
+{
+    // here, we list all JSON values from the RFC 7159 document
+
+    SECTION("7. Strings")
+    {
+        CHECK(json::parse("\"\\u005C\"") == json("\\"));
+        CHECK(json::parse("\"\\uD834\\uDD1E\"") == json("𝄞"));
+        CHECK(json::parse("\"𝄞\"") == json("𝄞"));
+    }
+
+    SECTION("8.3 String Comparison")
+    {
+        CHECK(json::parse("\"a\\b\"") == json::parse("\"a\u005Cb\""));
+    }
+
+    SECTION("13 Examples")
+    {
+        {
+            CHECK_NOTHROW(json(R"(
+            {
+                 "Image": {
+                     "Width":  800,
+                     "Height": 600,
+                     "Title":  "View from 15th Floor",
+                     "Thumbnail": {
+                         "Url":    "http://www.example.com/image/481989943",
+                         "Height": 125,
+                         "Width":  100
+                     },
+                     "Animated" : false,
+                     "IDs": [116, 943, 234, 38793]
+                   }
+               }
+            )"));
+        }
+
+        {
+            CHECK_NOTHROW(json(R"(
+                [
+                    {
+                       "precision": "zip",
+                       "Latitude":  37.7668,
+                       "Longitude": -122.3959,
+                       "Address":   "",
+                       "City":      "SAN FRANCISCO",
+                       "State":     "CA",
+                       "Zip":       "94107",
+                       "Country":   "US"
+                    },
+                    {
+                       "precision": "zip",
+                       "Latitude":  37.371991,
+                       "Longitude": -122.026020,
+                       "Address":   "",
+                       "City":      "SUNNYVALE",
+                       "State":     "CA",
+                       "Zip":       "94085",
+                       "Country":   "US"
+                    }
+            ])"));
+        }
+
+        CHECK(json::parse("\"Hello world!\"") == json("Hello world!"));
+        CHECK(json::parse("42") == json(42));
+        CHECK(json::parse("true") == json(true));
+    }
+}

test/src/unit-unicode.cpp

@@ -0,0 +1,176 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 2.0.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "catch.hpp"
+
+#define private public
+#include "json.hpp"
+using nlohmann::json;
+
+#include <fstream>
+
+TEST_CASE("Unicode", "[hide]")
+{
+    SECTION("full enumeration of Unicode code points")
+    {
+        // create an escaped string from a code point
+        const auto codepoint_to_unicode = [](std::size_t cp)
+        {
+            // copd points are represented as a six-character sequence: a
+            // reverse solidus, followed by the lowercase letter u, followed
+            // by four hexadecimal digits that encode the character's code
+            // point
+            std::stringstream ss;
+            ss << "\\u" << std::setw(4) << std::setfill('0') << std::hex << cp;
+            return ss.str();
+        };
+
+        // generate all UTF-8 code points; in total, 1112064 code points are
+        // generated: 0x1FFFFF code points - 2048 invalid values between
+        // 0xD800 and 0xDFFF.
+        for (std::size_t cp = 0; cp <= 0x10FFFFu; ++cp)
+        {
+            // The Unicode standard permanently reserves these code point
+            // values for UTF-16 encoding of the high and low surrogates, and
+            // they will never be assigned a character, so there should be no
+            // reason to encode them. The official Unicode standard says that
+            // no UTF forms, including UTF-16, can encode these code points.
+            if (cp >= 0xD800u and cp <= 0xDFFFu)
+            {
+                // if we would not skip these code points, we would get a
+                // "missing low surrogate" exception
+                continue;
+            }
+
+            // string to store the code point as in \uxxxx format
+            std::string escaped_string;
+            // string to store the code point as unescaped character sequence
+            std::string unescaped_string;
+
+            if (cp < 0x10000u)
+            {
+                // code points in the Basic Multilingual Plane can be
+                // represented with one \\uxxxx sequence
+                escaped_string = codepoint_to_unicode(cp);
+
+                // All Unicode characters may be placed within the quotation
+                // marks, except for the characters that must be escaped:
+                // quotation mark, reverse solidus, and the control characters
+                // (U+0000 through U+001F); we ignore these code points as
+                // they are checked with codepoint_to_unicode.
+                if (cp > 0x1f and cp != 0x22 and cp != 0x5c)
+                {
+                    unescaped_string = json::lexer::to_unicode(cp);
+                }
+            }
+            else
+            {
+                // To escape an extended character that is not in the Basic
+                // Multilingual Plane, the character is represented as a
+                // 12-character sequence, encoding the UTF-16 surrogate pair
+                const auto codepoint1 = 0xd800u + (((cp - 0x10000u) >> 10) & 0x3ffu);
+                const auto codepoint2 = 0xdc00u + ((cp - 0x10000u) & 0x3ffu);
+                escaped_string = codepoint_to_unicode(codepoint1);
+                escaped_string += codepoint_to_unicode(codepoint2);
+                unescaped_string += json::lexer::to_unicode(codepoint1, codepoint2);
+            }
+
+            // all other code points are valid and must not yield parse errors
+            CAPTURE(cp);
+            CAPTURE(escaped_string);
+            CAPTURE(unescaped_string);
+
+            json j1, j2, j3, j4;
+            CHECK_NOTHROW(j1 = json::parse("\"" + escaped_string + "\""));
+            CHECK_NOTHROW(j2 = json::parse(j1.dump()));
+            CHECK(j1 == j2);
+
+            CHECK_NOTHROW(j3 = json::parse("\"" + unescaped_string + "\""));
+            CHECK_NOTHROW(j4 = json::parse(j3.dump()));
+            CHECK(j3 == j4);
+        }
+    }
+
+    SECTION("read all unicode characters")
+    {
+        // read a file with all unicode characters stored as single-character
+        // strings in a JSON array
+        std::ifstream f("test/data/json_nlohmann_tests/all_unicode.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+
+        // the array has 1112064 + 1 elemnts (a terminating "null" value)
+        // Note: 1112064 = 0x1FFFFF code points - 2048 invalid values between
+        // 0xD800 and 0xDFFF.
+        CHECK(j.size() == 1112065);
+
+        SECTION("check JSON Pointers")
+        {
+            for (auto s : j)
+            {
+                // skip non-string JSON values
+                if (not s.is_string())
+                {
+                    continue;
+                }
+
+                std::string ptr = s;
+
+                // tilde must be followed by 0 or 1
+                if (ptr == "~")
+                {
+                    ptr += "0";
+                }
+
+                // JSON Pointers must begin with "/"
+                ptr = "/" + ptr;
+
+                CHECK_NOTHROW(json::json_pointer("/" + ptr));
+
+                // check escape/unescape roundtrip
+                auto escaped = json::json_pointer::escape(ptr);
+                json::json_pointer::unescape(escaped);
+                CHECK(escaped == ptr);
+            }
+        }
+    }
+
+    SECTION("ignore byte-order-mark")
+    {
+        // read a file with a UTF-8 BOM
+        std::ifstream f("test/data/json_nlohmann_tests/bom.json");
+        json j;
+        CHECK_NOTHROW(j << f);
+    }
+
+    SECTION("error for incomplete/wrong BOM")
+    {
+        CHECK_THROWS_AS(json::parse("\xef\xbb"), std::invalid_argument);
+        CHECK_THROWS_AS(json::parse("\xef\xbb\xbb"), std::invalid_argument);
+    }
+}