diff --git a/.github/ISSUE_TEMPLATE.md b/.github/ISSUE_TEMPLATE/Bug_report.md
similarity index 81%
rename from .github/ISSUE_TEMPLATE.md
rename to .github/ISSUE_TEMPLATE/Bug_report.md
index a3140bc1..177a4b39 100644
--- a/.github/ISSUE_TEMPLATE.md
+++ b/.github/ISSUE_TEMPLATE/Bug_report.md
@@ -1,22 +1,19 @@
-**Bug Report**
-
-- What is the issue you have?
-
-- Please describe the steps to reproduce the issue. Can you provide a small but working code example?
-
-- What is the expected behavior?
-
-- And what is the actual behavior instead?
-
-- Which compiler and operating system are you using? Is it a [supported compiler](https://github.com/nlohmann/json#supported-compilers)?
-
-- Did you use a released version of the library or the version from the `develop` branch?
-
-- If you experience a compilation error: can you [compile and run the unit tests](https://github.com/nlohmann/json#execute-unit-tests)?
-
-
-**Feature Request**
-
-- Describe the feature in as much detail as possible.
-
-- Include sample usage where appropriate.
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+- What is the issue you have?
+
+- Please describe the steps to reproduce the issue. Can you provide a small but working code example?
+
+- What is the expected behavior?
+
+- And what is the actual behavior instead?
+
+- Which compiler and operating system are you using? Is it a [supported compiler](https://github.com/nlohmann/json#supported-compilers)?
+
+- Did you use a released version of the library or the version from the `develop` branch?
+
+- If you experience a compilation error: can you [compile and run the unit tests](https://github.com/nlohmann/json#execute-unit-tests)?
diff --git a/.github/ISSUE_TEMPLATE/Feature_request.md b/.github/ISSUE_TEMPLATE/Feature_request.md
new file mode 100644
index 00000000..f5ea57ca
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/Feature_request.md
@@ -0,0 +1,9 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+
+---
+
+- Describe the feature in as much detail as possible.
+
+- Include sample usage where appropriate.
diff --git a/.travis.yml b/.travis.yml
index 68a16db5..ecc8c362 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -155,6 +155,9 @@ matrix:
   - os: osx
     osx_image: xcode9.2
 
+  - os: osx
+    osx_image: xcode9.3
+
   # Linux / GCC
 
   - os: linux
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a490ab6b..031a66f2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,13 +22,15 @@ option(JSON_MultipleHeaders "Use non-amalgamated version of the library." OFF)
 ## CONFIGURATION
 ##
 set(NLOHMANN_JSON_TARGET_NAME               ${PROJECT_NAME})
-set(NLOHMANN_JSON_CONFIG_INSTALL_DIR        "lib/cmake/${PROJECT_NAME}")
+set(NLOHMANN_JSON_CONFIG_INSTALL_DIR        "lib/cmake/${PROJECT_NAME}"
+  CACHE INTERNAL "")
 set(NLOHMANN_JSON_INCLUDE_INSTALL_DIR       "include")
 set(NLOHMANN_JSON_TARGETS_EXPORT_NAME       "${PROJECT_NAME}Targets")
 set(NLOHMANN_JSON_CMAKE_CONFIG_TEMPLATE     "cmake/config.cmake.in")
-set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}/cmake_config")
+set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}")
 set(NLOHMANN_JSON_CMAKE_VERSION_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}ConfigVersion.cmake")
 set(NLOHMANN_JSON_CMAKE_PROJECT_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Config.cmake")
+set(NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Targets.cmake")
 
 if (JSON_MultipleHeaders)
     set(NLOHMANN_JSON_INCLUDE_BUILD_DIR "${PROJECT_SOURCE_DIR}/include/")
@@ -43,7 +45,7 @@ endif()
 ## create target and add include path
 ##
 add_library(${NLOHMANN_JSON_TARGET_NAME} INTERFACE)
-
+add_library(${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} ALIAS ${NLOHMANN_JSON_TARGET_NAME})
 target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_std_11)
 
 target_include_directories(
@@ -53,7 +55,7 @@ target_include_directories(
     $<INSTALL_INTERFACE:include>
 )
 
-## add debug view defintion file for msvc (natvis)
+## add debug view definition file for msvc (natvis)
 if (MSVC)
     set(NLOHMANN_ADD_NATVIS TRUE)
     set(NLOHMANN_NATVIS_FILE "nlohmann_json.natvis")
@@ -104,6 +106,11 @@ if (NLOHMANN_ADD_NATVIS)
         DESTINATION .
 )
 endif()
+export(
+    TARGETS ${NLOHMANN_JSON_TARGET_NAME}
+    NAMESPACE ${PROJECT_NAME}::
+    FILE ${NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE}
+)
 install(
     TARGETS ${NLOHMANN_JSON_TARGET_NAME}
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
@@ -111,5 +118,6 @@ install(
 )
 install(
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
+    NAMESPACE ${PROJECT_NAME}::
     DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
 )
diff --git a/README.md b/README.md
index e2e180d7..74710bfe 100644
--- a/README.md
+++ b/README.md
@@ -834,7 +834,8 @@ The following compilers are currently used in continuous integration at [Travis]
 | Clang Xcode 8.3 | Darwin Kernel Version 16.5.0 (macOS 10.12.4) | Apple LLVM version 8.1.0 (clang-802.0.38) |
 | Clang Xcode 9.0 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.37) |
 | Clang Xcode 9.1 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.38) |
-| Clang Xcode 9.2 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 8.1.0 (clang-900.0.39.2) |
+| Clang Xcode 9.2 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.39.2) |
+| Clang Xcode 9.3 | Darwin Kernel Version 17.4.0 (macOS 10.13.0) | Apple LLVM version 9.1.0 (clang-902.0.39.1)
 | Visual Studio 14 2015 | Windows Server 2012 R2 (x64) | Microsoft (R) Build Engine version 14.0.25420.1, MSVC 19.0.24215.1 |
 | Visual Studio 2017 | Windows Server 2016 | Microsoft (R) Build Engine version 15.5.180.51428, MSVC 19.12.25830.2 |
 
@@ -864,6 +865,10 @@ If you have questions regarding the library, I would like to invite you to [open
 
 Only if your request would contain confidential information, please [send me an email](mailto:mail@nlohmann.me). For encrypted messages, please use [this key](https://keybase.io/nlohmann/pgp_keys.asc).
 
+## Security
+
+[Commits by Niels Lohmann](https://github.com/nlohmann/json/commits) and [releases](https://github.com/nlohmann/json/releases) are signed with this [PGP Key](https://keybase.io/nlohmann/pgp_keys.asc?fingerprint=797167ae41c0a6d9232e48457f3cea63ae251b69).
+
 
 ## Thanks
 
@@ -977,14 +982,19 @@ I deeply appreciate the help of the following people.
 - [Paul Fultz II](https://github.com/pfultz2) added a note on the cget package manager.
 - [Wilson Lin](https://github.com/wla80) made the integration section of the README more concise.
 - [RalfBielig](https://github.com/ralfbielig) detected and fixed a memory leak in the parser callback.
-- [agrianius](https://github.com/agrianius) allowed to dump JSON to an alternative string type
+- [agrianius](https://github.com/agrianius) allowed to dump JSON to an alternative string type.
+- [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake.
+- [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io).
+- [Carlos O'Ryan](https://github.com/coryan) fixed a typo.
+- [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section.
+- [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines
 
 Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.
 
 
 ## Used third-party tools
 
-The library itself contains of a single header file licensed under the MIT license. However, it is built, tested, documented, and whatnot using a lot of third-party tools and services. Thanks a lot!
+The library itself consists of a single header file licensed under the MIT license. However, it is built, tested, documented, and whatnot using a lot of third-party tools and services. Thanks a lot!
 
 - [**amalgamate.py - Amalgamate C source and header files**](https://github.com/edlund/amalgamate) to create a single header file
 - [**American fuzzy lop**](http://lcamtuf.coredump.cx/afl/) for fuzz testing
diff --git a/cmake/config.cmake.in b/cmake/config.cmake.in
index b4fd29d9..8baabf07 100644
--- a/cmake/config.cmake.in
+++ b/cmake/config.cmake.in
@@ -1,3 +1,5 @@
 @PACKAGE_INIT@
-include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
+if(NOT TARGET @PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@)
+    include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
+endif()
 check_required_components("@PROJECT_NAME@")
diff --git a/doc/avatars.png b/doc/avatars.png
index 00241908..4d557d28 100644
Binary files a/doc/avatars.png and b/doc/avatars.png differ
diff --git a/include/nlohmann/detail/input/input_adapters.hpp b/include/nlohmann/detail/input/input_adapters.hpp
index 4c942f33..6a3ffa2b 100644
--- a/include/nlohmann/detail/input/input_adapters.hpp
+++ b/include/nlohmann/detail/input/input_adapters.hpp
@@ -115,6 +115,176 @@ class input_buffer_adapter : public input_adapter_protocol
     const char* const limit;
 };
 
+template<typename WideStringType>
+class wide_string_input_adapter : public input_adapter_protocol
+{
+  public:
+    wide_string_input_adapter(const WideStringType& w) : str(w) {}
+
+    std::char_traits<char>::int_type get_character() noexcept override
+    {
+        // unget_character() was called previously: return the last character
+        if (next_unget)
+        {
+            next_unget = false;
+            return last_char;
+        }
+
+        // check if buffer needs to be filled
+        if (utf8_bytes_index == utf8_bytes_filled)
+        {
+            if (sizeof(typename WideStringType::value_type) == 2)
+            {
+                fill_buffer_utf16();
+            }
+            else
+            {
+                fill_buffer_utf32();
+            }
+
+            assert(utf8_bytes_filled > 0);
+            assert(utf8_bytes_index == 0);
+        }
+
+        // use buffer
+        assert(utf8_bytes_filled > 0);
+        assert(utf8_bytes_index < utf8_bytes_filled);
+        return (last_char = utf8_bytes[utf8_bytes_index++]);
+    }
+
+    void unget_character() noexcept override
+    {
+        next_unget = true;
+    }
+
+  private:
+    void fill_buffer_utf16()
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-16 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6));
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (0xD800 > wc or wc >= 0xE000)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12));
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else
+            {
+                if (current_wchar < str.size())
+                {
+                    const int wc2 = static_cast<int>(str[current_wchar++]);
+                    const int charcode = 0x10000 + (((wc & 0x3FF) << 10) | (wc2 & 0x3FF));
+                    utf8_bytes[0] = 0xf0 | (charcode >> 18);
+                    utf8_bytes[1] = 0x80 | ((charcode >> 12) & 0x3F);
+                    utf8_bytes[2] = 0x80 | ((charcode >> 6) & 0x3F);
+                    utf8_bytes[3] = 0x80 | (charcode & 0x3F);
+                    utf8_bytes_filled = 4;
+                }
+                else
+                {
+                    // unknown character
+                    ++current_wchar;
+                    utf8_bytes[0] = wc;
+                    utf8_bytes_filled = 1;
+                }
+            }
+        }
+    }
+
+    void fill_buffer_utf32()
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-32 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6) & 0x1F);
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (wc <= 0xFFFF)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12) & 0x0F);
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else if (wc <= 0x10FFFF)
+            {
+                utf8_bytes[0] = 0xF0 | ((wc >> 18 ) & 0x07);
+                utf8_bytes[1] = 0x80 | ((wc >> 12) & 0x3F);
+                utf8_bytes[2] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[3] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 4;
+            }
+            else
+            {
+                // unknown character
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+        }
+    }
+
+  private:
+    /// the wstring to process
+    const WideStringType& str;
+
+    /// index of the current wchar in str
+    std::size_t current_wchar = 0;
+
+    /// a buffer for UTF-8 bytes
+    std::array<std::char_traits<char>::int_type, 4> utf8_bytes = {{0, 0, 0, 0}};
+
+    /// index to the utf8_codes array for the next valid byte
+    std::size_t utf8_bytes_index = 0;
+    /// number of valid bytes in the utf8_codes array
+    std::size_t utf8_bytes_filled = 0;
+
+    /// the last character (returned after unget_character() is called)
+    std::char_traits<char>::int_type last_char = 0;
+    /// whether get_character() should return last_char
+    bool next_unget = false;
+};
+
 class input_adapter
 {
   public:
@@ -128,6 +298,15 @@ class input_adapter
     input_adapter(std::istream&& i)
         : ia(std::make_shared<input_stream_adapter>(i)) {}
 
+    input_adapter(const std::wstring& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::wstring>>(ws)) {}
+
+    input_adapter(const std::u16string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u16string>>(ws)) {}
+
+    input_adapter(const std::u32string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u32string>>(ws)) {}
+
     /// input adapter for buffer
     template<typename CharT,
              typename std::enable_if<
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 66d0fb37..f5b93632 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -3412,7 +3413,7 @@ class basic_json
     @return copy of the element at key @a key or @a default_value if @a key
     is not found
 
-    @throw type_error.306 if the JSON value is not an objec; in that case,
+    @throw type_error.306 if the JSON value is not an object; in that case,
     using `value()` with a key makes no sense.
 
     @complexity Logarithmic in the size of the container.
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 8558651d..fa7f585d 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -1688,6 +1689,176 @@ class input_buffer_adapter : public input_adapter_protocol
     const char* const limit;
 };
 
+template<typename WideStringType>
+class wide_string_input_adapter : public input_adapter_protocol
+{
+  public:
+    wide_string_input_adapter(const WideStringType& w) : str(w) {}
+
+    std::char_traits<char>::int_type get_character() noexcept override
+    {
+        // unget_character() was called previously: return the last character
+        if (next_unget)
+        {
+            next_unget = false;
+            return last_char;
+        }
+
+        // check if buffer needs to be filled
+        if (utf8_bytes_index == utf8_bytes_filled)
+        {
+            if (sizeof(typename WideStringType::value_type) == 2)
+            {
+                fill_buffer_utf16();
+            }
+            else
+            {
+                fill_buffer_utf32();
+            }
+
+            assert(utf8_bytes_filled > 0);
+            assert(utf8_bytes_index == 0);
+        }
+
+        // use buffer
+        assert(utf8_bytes_filled > 0);
+        assert(utf8_bytes_index < utf8_bytes_filled);
+        return (last_char = utf8_bytes[utf8_bytes_index++]);
+    }
+
+    void unget_character() noexcept override
+    {
+        next_unget = true;
+    }
+
+  private:
+    void fill_buffer_utf16()
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-16 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6));
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (0xD800 > wc or wc >= 0xE000)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12));
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else
+            {
+                if (current_wchar < str.size())
+                {
+                    const int wc2 = static_cast<int>(str[current_wchar++]);
+                    const int charcode = 0x10000 + (((wc & 0x3FF) << 10) | (wc2 & 0x3FF));
+                    utf8_bytes[0] = 0xf0 | (charcode >> 18);
+                    utf8_bytes[1] = 0x80 | ((charcode >> 12) & 0x3F);
+                    utf8_bytes[2] = 0x80 | ((charcode >> 6) & 0x3F);
+                    utf8_bytes[3] = 0x80 | (charcode & 0x3F);
+                    utf8_bytes_filled = 4;
+                }
+                else
+                {
+                    // unknown character
+                    ++current_wchar;
+                    utf8_bytes[0] = wc;
+                    utf8_bytes_filled = 1;
+                }
+            }
+        }
+    }
+
+    void fill_buffer_utf32()
+    {
+        utf8_bytes_index = 0;
+
+        if (current_wchar == str.size())
+        {
+            utf8_bytes[0] = std::char_traits<char>::eof();
+            utf8_bytes_filled = 1;
+        }
+        else
+        {
+            // get the current character
+            const int wc = static_cast<int>(str[current_wchar++]);
+
+            // UTF-32 to UTF-8 encoding
+            if (wc < 0x80)
+            {
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+            else if (wc <= 0x7FF)
+            {
+                utf8_bytes[0] = 0xC0 | ((wc >> 6) & 0x1F);
+                utf8_bytes[1] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 2;
+            }
+            else if (wc <= 0xFFFF)
+            {
+                utf8_bytes[0] = 0xE0 | ((wc >> 12) & 0x0F);
+                utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[2] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 3;
+            }
+            else if (wc <= 0x10FFFF)
+            {
+                utf8_bytes[0] = 0xF0 | ((wc >> 18 ) & 0x07);
+                utf8_bytes[1] = 0x80 | ((wc >> 12) & 0x3F);
+                utf8_bytes[2] = 0x80 | ((wc >> 6) & 0x3F);
+                utf8_bytes[3] = 0x80 | (wc & 0x3F);
+                utf8_bytes_filled = 4;
+            }
+            else
+            {
+                // unknown character
+                utf8_bytes[0] = wc;
+                utf8_bytes_filled = 1;
+            }
+        }
+    }
+
+  private:
+    /// the wstring to process
+    const WideStringType& str;
+
+    /// index of the current wchar in str
+    std::size_t current_wchar = 0;
+
+    /// a buffer for UTF-8 bytes
+    std::array<std::char_traits<char>::int_type, 4> utf8_bytes = {{0, 0, 0, 0}};
+
+    /// index to the utf8_codes array for the next valid byte
+    std::size_t utf8_bytes_index = 0;
+    /// number of valid bytes in the utf8_codes array
+    std::size_t utf8_bytes_filled = 0;
+
+    /// the last character (returned after unget_character() is called)
+    std::char_traits<char>::int_type last_char = 0;
+    /// whether get_character() should return last_char
+    bool next_unget = false;
+};
+
 class input_adapter
 {
   public:
@@ -1701,6 +1872,15 @@ class input_adapter
     input_adapter(std::istream&& i)
         : ia(std::make_shared<input_stream_adapter>(i)) {}
 
+    input_adapter(const std::wstring& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::wstring>>(ws)) {}
+
+    input_adapter(const std::u16string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u16string>>(ws)) {}
+
+    input_adapter(const std::u32string& ws)
+        : ia(std::make_shared<wide_string_input_adapter<std::u32string>>(ws)) {}
+
     /// input adapter for buffer
     template<typename CharT,
              typename std::enable_if<
@@ -13934,7 +14114,7 @@ class basic_json
     @return copy of the element at key @a key or @a default_value if @a key
     is not found
 
-    @throw type_error.306 if the JSON value is not an objec; in that case,
+    @throw type_error.306 if the JSON value is not an object; in that case,
     using `value()` with a key makes no sense.
 
     @complexity Logarithmic in the size of the container.
diff --git a/test/Makefile b/test/Makefile
index f373451f..afbb1ba5 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -42,7 +42,8 @@ SOURCES = src/unit.cpp \
           src/unit-serialization.cpp \
           src/unit-testsuites.cpp \
           src/unit-ubjson.cpp \
-          src/unit-unicode.cpp
+          src/unit-unicode.cpp \
+          src/unit-wstring.cpp
 
 OBJECTS = $(SOURCES:.cpp=.o)
 
diff --git a/test/src/unit-algorithms.cpp b/test/src/unit-algorithms.cpp
index 6579c4a5..b9747b9b 100644
--- a/test/src/unit-algorithms.cpp
+++ b/test/src/unit-algorithms.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-allocator.cpp b/test/src/unit-allocator.cpp
index debe69ad..2566d298 100644
--- a/test/src/unit-allocator.cpp
+++ b/test/src/unit-allocator.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -175,29 +176,6 @@ TEST_CASE("controlled bad_alloc")
             CHECK_THROWS_AS(my_json::json_value(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")
diff --git a/test/src/unit-alt-string.cpp b/test/src/unit-alt-string.cpp
index 36c8b83b..cc05039c 100644
--- a/test/src/unit-alt-string.cpp
+++ b/test/src/unit-alt-string.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2018 Vitaliy Manushkin <agri@akamo.info>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-capacity.cpp b/test/src/unit-capacity.cpp
index 47ac03cc..3cdaed92 100644
--- a/test/src/unit-capacity.cpp
+++ b/test/src/unit-capacity.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-cbor.cpp b/test/src/unit-cbor.cpp
index 29879508..21235b0d 100644
--- a/test/src/unit-cbor.cpp
+++ b/test/src/unit-cbor.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -575,7 +576,6 @@ TEST_CASE("CBOR")
                     }
                 }
 
-                /*
                 SECTION("-32768..-129 (int 16)")
                 {
                     for (int16_t i = -32768; i <= -129; ++i)
@@ -601,14 +601,13 @@ TEST_CASE("CBOR")
 
                         // check individual bytes
                         CHECK(result[0] == 0xd1);
-                        int16_t restored = (result[1] << 8) + result[2];
+                        int16_t restored = static_cast<int16_t>((result[1] << 8) + result[2]);
                         CHECK(restored == i);
 
                         // roundtrip
                         CHECK(json::from_msgpack(result) == j);
                     }
                 }
-                */
             }
 
             SECTION("unsigned")
@@ -1147,28 +1146,6 @@ TEST_CASE("CBOR")
                 CHECK(json::from_cbor(result) == j);
                 CHECK(json::from_cbor(result, true, false) == j);
             }
-
-            /*
-            SECTION("array with uint64_t elements")
-            {
-                json j(4294967296, nullptr);
-                std::vector<uint8_t> expected(j.size() + 9, 0xf6); // all null
-                expected[0] = 0x9b; // array 64 bit
-                expected[1] = 0x00; // size (0x0000000100000000), byte 0
-                expected[2] = 0x00; // size (0x0000000100000000), byte 1
-                expected[3] = 0x00; // size (0x0000000100000000), byte 2
-                expected[4] = 0x01; // size (0x0000000100000000), byte 3
-                expected[5] = 0x00; // size (0x0000000100000000), byte 4
-                expected[6] = 0x00; // size (0x0000000100000000), byte 5
-                expected[7] = 0x00; // size (0x0000000100000000), byte 6
-                expected[8] = 0x00; // size (0x0000000100000000), byte 7
-                const auto result = json::to_cbor(j);
-                CHECK(result == expected);
-
-                // roundtrip
-                CHECK(json::from_cbor(result) == j);
-            }
-            */
         }
 
         SECTION("object")
diff --git a/test/src/unit-class_const_iterator.cpp b/test/src/unit-class_const_iterator.cpp
index 8319fef5..20cc7529 100644
--- a/test/src/unit-class_const_iterator.cpp
+++ b/test/src/unit-class_const_iterator.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-class_iterator.cpp b/test/src/unit-class_iterator.cpp
index 484a49de..07218d9f 100644
--- a/test/src/unit-class_iterator.cpp
+++ b/test/src/unit-class_iterator.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-class_lexer.cpp b/test/src/unit-class_lexer.cpp
index 164dc67d..35338a80 100644
--- a/test/src/unit-class_lexer.cpp
+++ b/test/src/unit-class_lexer.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -173,15 +174,4 @@ TEST_CASE("lexer class")
         s += "\"";
         CHECK((scan_string(s.c_str()) == json::lexer::token_type::value_string));
     }
-
-    /* NOTE: to_unicode function has been removed
-    SECTION("to_unicode")
-    {
-        // lexer to call to_unicode on
-        json::lexer dummy_lexer("", 0);
-        CHECK(dummy_lexer.to_unicode(0x1F4A9) == "💩");
-        CHECK_THROWS_AS(dummy_lexer.to_unicode(0x200000), json::parse_error);
-        CHECK_THROWS_WITH(dummy_lexer.to_unicode(0x200000), "[json.exception.parse_error.103] parse error: code points above 0x10FFFF are invalid");
-    }
-    */
 }
diff --git a/test/src/unit-class_parser.cpp b/test/src/unit-class_parser.cpp
index e4cfb536..6edb0a2e 100644
--- a/test/src/unit-class_parser.cpp
+++ b/test/src/unit-class_parser.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-comparison.cpp b/test/src/unit-comparison.cpp
index 0659c1db..da394407 100644
--- a/test/src/unit-comparison.cpp
+++ b/test/src/unit-comparison.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-concepts.cpp b/test/src/unit-concepts.cpp
index e2aac157..735ca0cb 100644
--- a/test/src/unit-concepts.cpp
+++ b/test/src/unit-concepts.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-constructor1.cpp b/test/src/unit-constructor1.cpp
index 35652bd8..bba24b71 100644
--- a/test/src/unit-constructor1.cpp
+++ b/test/src/unit-constructor1.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-constructor2.cpp b/test/src/unit-constructor2.cpp
index e36de923..120cb06b 100644
--- a/test/src/unit-constructor2.cpp
+++ b/test/src/unit-constructor2.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-convenience.cpp b/test/src/unit-convenience.cpp
index 15596032..6711fdd9 100644
--- a/test/src/unit-convenience.cpp
+++ b/test/src/unit-convenience.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-conversions.cpp b/test/src/unit-conversions.cpp
index d67f5acb..351dec8a 100644
--- a/test/src/unit-conversions.cpp
+++ b/test/src/unit-conversions.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-deserialization.cpp b/test/src/unit-deserialization.cpp
index d69c5983..09d5395a 100644
--- a/test/src/unit-deserialization.cpp
+++ b/test/src/unit-deserialization.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-element_access1.cpp b/test/src/unit-element_access1.cpp
index d06b97ca..af7818c4 100644
--- a/test/src/unit-element_access1.cpp
+++ b/test/src/unit-element_access1.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-element_access2.cpp b/test/src/unit-element_access2.cpp
index 5ea4b8a5..eb0d943f 100644
--- a/test/src/unit-element_access2.cpp
+++ b/test/src/unit-element_access2.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-inspection.cpp b/test/src/unit-inspection.cpp
index 111e6ea2..4c03cf96 100644
--- a/test/src/unit-inspection.cpp
+++ b/test/src/unit-inspection.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-items.cpp b/test/src/unit-items.cpp
index 8f18884d..579e1141 100644
--- a/test/src/unit-items.cpp
+++ b/test/src/unit-items.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-iterators1.cpp b/test/src/unit-iterators1.cpp
index c8125ce7..ef8d3185 100644
--- a/test/src/unit-iterators1.cpp
+++ b/test/src/unit-iterators1.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-iterators2.cpp b/test/src/unit-iterators2.cpp
index 2d369881..b3e1b820 100644
--- a/test/src/unit-iterators2.cpp
+++ b/test/src/unit-iterators2.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-json_patch.cpp b/test/src/unit-json_patch.cpp
index 1a71621d..d2079b4e 100644
--- a/test/src/unit-json_patch.cpp
+++ b/test/src/unit-json_patch.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-json_pointer.cpp b/test/src/unit-json_pointer.cpp
index c630da56..ec49e114 100644
--- a/test/src/unit-json_pointer.cpp
+++ b/test/src/unit-json_pointer.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-merge_patch.cpp b/test/src/unit-merge_patch.cpp
index 2daaf00f..7e36c432 100644
--- a/test/src/unit-merge_patch.cpp
+++ b/test/src/unit-merge_patch.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-meta.cpp b/test/src/unit-meta.cpp
index 6fc84998..db03453a 100644
--- a/test/src/unit-meta.cpp
+++ b/test/src/unit-meta.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-modifiers.cpp b/test/src/unit-modifiers.cpp
index ada65f20..1092dae3 100644
--- a/test/src/unit-modifiers.cpp
+++ b/test/src/unit-modifiers.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-msgpack.cpp b/test/src/unit-msgpack.cpp
index 7789ccb7..b10afbf4 100644
--- a/test/src/unit-msgpack.cpp
+++ b/test/src/unit-msgpack.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-noexcept.cpp b/test/src/unit-noexcept.cpp
index 4b3dcade..2d49b327 100644
--- a/test/src/unit-noexcept.cpp
+++ b/test/src/unit-noexcept.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-pointer_access.cpp b/test/src/unit-pointer_access.cpp
index 5670269a..fe56efbd 100644
--- a/test/src/unit-pointer_access.cpp
+++ b/test/src/unit-pointer_access.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-readme.cpp b/test/src/unit-readme.cpp
index 4c163afa..974adeaf 100644
--- a/test/src/unit-readme.cpp
+++ b/test/src/unit-readme.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-reference_access.cpp b/test/src/unit-reference_access.cpp
index 3c92096f..43a096a7 100644
--- a/test/src/unit-reference_access.cpp
+++ b/test/src/unit-reference_access.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-regression.cpp b/test/src/unit-regression.cpp
index 01e68957..8bdd2dc3 100644
--- a/test/src/unit-regression.cpp
+++ b/test/src/unit-regression.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -136,19 +137,19 @@ TEST_CASE("regression tests")
 
     SECTION("issue #70 - Handle infinity and NaN cases")
     {
-        /*
+        // previously, NAN/INFINITY created a null value; now, the values are
+        // properly stored, but are dumped as "null"
         SECTION("NAN value")
         {
-            CHECK(json(NAN) == json());
-            CHECK(json(json::number_float_t(NAN)) == json());
+            CHECK(json(NAN).dump() == "null");
+            CHECK(json(json::number_float_t(NAN)).dump() == "null");
         }
 
         SECTION("infinity")
         {
-            CHECK(json(INFINITY) == json());
-            CHECK(json(json::number_float_t(INFINITY)) == json());
+            CHECK(json(INFINITY).dump() == "null");
+            CHECK(json(json::number_float_t(INFINITY)).dump() == "null");
         }
-        */
 
         // With 3.0.0, the semantics of this changed: NAN and infinity are
         // stored properly inside the JSON value (no exception or conversion
@@ -1213,41 +1214,6 @@ TEST_CASE("regression tests")
         CHECK(j["bool_vector"].dump() == "[false,true,false,false]");
     }
 
-    /* NOTE: m_line_buffer is not used any more
-    SECTION("issue #495 - fill_line_buffer incorrectly tests m_stream for eof but not fail or bad bits")
-    {
-        SECTION("setting failbit")
-        {
-            std::stringstream ss;
-            ss << "[1,2,3\n,4,5]";
-
-            json::lexer l(ss);
-
-            CHECK(l.m_line_buffer == "[1,2,3\n");
-
-            l.m_stream->setstate(std::ios_base::failbit);
-
-            CHECK_THROWS_AS(l.fill_line_buffer(), json::parse_error&);
-            CHECK_THROWS_WITH(l.fill_line_buffer(), "[json.exception.parse_error.111] parse error: bad input stream");
-        }
-
-        SECTION("setting badbit")
-        {
-            std::stringstream ss;
-            ss << "[1,2,3\n,4,5]";
-
-            json::lexer l(ss);
-
-            CHECK(l.m_line_buffer == "[1,2,3\n");
-
-            l.m_stream->setstate(std::ios_base::badbit);
-
-            CHECK_THROWS_AS(l.fill_line_buffer(), json::parse_error&);
-            CHECK_THROWS_WITH(l.fill_line_buffer(), "[json.exception.parse_error.111] parse error: bad input stream");
-        }
-    }
-     */
-
     SECTION("issue #504 - assertion error (OSS-Fuzz 856)")
     {
         std::vector<uint8_t> vec1 = {0xf9, 0xff, 0xff, 0x4a, 0x3a, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0x37, 0x02, 0x38};
diff --git a/test/src/unit-serialization.cpp b/test/src/unit-serialization.cpp
index ebe64297..3abc7fb1 100644
--- a/test/src/unit-serialization.cpp
+++ b/test/src/unit-serialization.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-testsuites.cpp b/test/src/unit-testsuites.cpp
index 5f77a737..a668abd5 100644
--- a/test/src/unit-testsuites.cpp
+++ b/test/src/unit-testsuites.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-to_chars.cpp b/test/src/unit-to_chars.cpp
index 841e164b..fc86f30f 100644
--- a/test/src/unit-to_chars.cpp
+++ b/test/src/unit-to_chars.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-ubjson.cpp b/test/src/unit-ubjson.cpp
index 791668ff..0e15c164 100644
--- a/test/src/unit-ubjson.cpp
+++ b/test/src/unit-ubjson.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
@@ -1803,257 +1804,6 @@ TEST_CASE("UBJSON")
     }
 }
 
-/*
-// use this testcase outside [hide] to run it with Valgrind
-TEST_CASE("single UBJSON roundtrip")
-{
-    SECTION("sample.json")
-    {
-        std::string filename = "test/data/json_testsuite/sample.json";
-
-        // parse JSON file
-        std::ifstream f_json(filename);
-        json j1 = json::parse(f_json);
-
-        // parse MessagePack file
-        std::ifstream f_ubjson(filename + ".ubj", std::ios::binary);
-        std::vector<uint8_t> packed((std::istreambuf_iterator<char>(f_ubjson)),
-                                    std::istreambuf_iterator<char>());
-        json j2;
-        CHECK_NOTHROW(j2 = json::from_ubjson(packed));
-
-        // compare parsed JSON values
-        CHECK(j1 == j2);
-
-        SECTION("roundtrips")
-        {
-            SECTION("std::ostringstream")
-            {
-                std::ostringstream ss;
-                json::to_ubjson(j1, ss);
-                json j3 = json::from_ubjson(ss.str());
-                CHECK(j1 == j3);
-            }
-
-            SECTION("std::string")
-            {
-                std::string s;
-                json::to_ubjson(j1, s);
-                json j3 = json::from_ubjson(s);
-                CHECK(j1 == j3);
-            }
-        }
-
-        // check with different start index
-        // packed.insert(packed.begin(), 5, 0xff);
-        // CHECK(j1 == json::from_ubjson(packed.begin() + 5, packed.end()));
-    }
-}
-*/
-
-/*
-TEST_CASE("UBJSON roundtrips", "[hide]")
-{
-    SECTION("input from py-ubjson")
-    {
-        for (std::string filename :
-                {
-                    "test/data/json_nlohmann_tests/all_unicode.json",
-                    "test/data/json.org/1.json",
-                    "test/data/json.org/2.json",
-                    "test/data/json.org/3.json",
-                    "test/data/json.org/4.json",
-                    "test/data/json.org/5.json",
-                    "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",
-                    "test/data/json_roundtrip/roundtrip25.json",
-                    "test/data/json_roundtrip/roundtrip26.json",
-                    "test/data/json_roundtrip/roundtrip27.json",
-                    "test/data/json_roundtrip/roundtrip28.json",
-                    "test/data/json_roundtrip/roundtrip29.json",
-                    "test/data/json_roundtrip/roundtrip30.json",
-                    "test/data/json_roundtrip/roundtrip31.json",
-                    "test/data/json_roundtrip/roundtrip32.json",
-                    "test/data/json_testsuite/sample.json", // kills AppVeyor
-                    "test/data/json_tests/pass1.json",
-                    "test/data/json_tests/pass2.json",
-                    "test/data/json_tests/pass3.json",
-                    "test/data/regression/floats.json",
-                    "test/data/regression/signed_ints.json",
-                    "test/data/regression/unsigned_ints.json",
-                    "test/data/regression/working_file.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_arraysWithSpaces.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_empty-string.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_empty.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_ending_with_newline.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_false.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_heterogeneous.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_null.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_with_1_and_newline.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_with_leading_space.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_with_several_null.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_array_with_trailing_space.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_0e+1.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_0e1.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_after_space.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_double_close_to_zero.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_double_huge_neg_exp.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_huge_exp.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_int_with_exp.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_minus_zero.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_negative_int.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_negative_one.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_negative_zero.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_capital_e.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_capital_e_neg_exp.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_capital_e_pos_exp.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_exponent.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_fraction_exponent.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_neg_exp.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_real_neg_overflow.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_pos_exponent.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_real_pos_overflow.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_real_underflow.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_simple_int.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_number_simple_real.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_too_big_neg_int.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_too_big_pos_int.json",
-                    //"test/data/nst_json_testsuite/test_parsing/y_number_very_big_negative_int.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_basic.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_duplicated_key.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_duplicated_key_and_value.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_empty.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_empty_key.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_escaped_null_in_key.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_extreme_numbers.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_long_strings.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_simple.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_string_unicode.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_object_with_newlines.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_1_2_3_bytes_UTF-8_sequences.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_UTF-16_Surrogates_U+1D11E_MUSICAL_SYMBOL_G_CLEF.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_accepted_surrogate_pair.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_accepted_surrogate_pairs.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_allowed_escapes.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_backslash_and_u_escaped_zero.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_backslash_doublequotes.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_comments.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_double_escape_a.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_double_escape_n.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_escaped_control_character.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_escaped_noncharacter.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_in_array.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_in_array_with_leading_space.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_last_surrogates_1_and_2.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_newline_uescaped.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_nonCharacterInUTF-8_U+10FFFF.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_nonCharacterInUTF-8_U+1FFFF.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_nonCharacterInUTF-8_U+FFFF.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_null_escape.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_one-byte-utf-8.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_pi.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_simple_ascii.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_space.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_three-byte-utf-8.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_two-byte-utf-8.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_u+2028_line_sep.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_u+2029_par_sep.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_uEscape.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unescaped_char_delete.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicode.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicodeEscapedBackslash.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicode_2.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicode_U+200B_ZERO_WIDTH_SPACE.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicode_U+2064_invisible_plus.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_unicode_escaped_double_quote.json",
-                    // "test/data/nst_json_testsuite/test_parsing/y_string_utf16.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_utf8.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_string_with_del_character.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_false.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_int.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_negative_real.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_null.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_string.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_lonely_true.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_string_empty.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_trailing_newline.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_true_in_array.json",
-                    "test/data/nst_json_testsuite/test_parsing/y_structure_whitespace_array.json"
-                })
-        {
-            CAPTURE(filename);
-
-            // parse JSON file
-            std::ifstream f_json(filename);
-            json j1 = json::parse(f_json);
-
-            SECTION("std::vector<uint8_t>")
-            {
-                // parse UBJSON file
-                std::ifstream f_ubjson(filename + ".ubj", std::ios::binary);
-                std::vector<uint8_t> packed(
-                    (std::istreambuf_iterator<char>(f_ubjson)),
-                    std::istreambuf_iterator<char>());
-                json j2;
-                CHECK_NOTHROW(j2 = json::from_ubjson(packed));
-
-                // compare parsed JSON values
-                CHECK(j1 == j2);
-            }
-
-            SECTION("std::ifstream")
-            {
-                // parse UBJSON file
-                std::ifstream f_ubjson(filename + ".ubj", std::ios::binary);
-                json j2;
-                CHECK_NOTHROW(j2 = json::from_ubjson(f_ubjson));
-
-                // compare parsed JSON values
-                CHECK(j1 == j2);
-            }
-
-            SECTION("uint8_t* and size")
-            {
-                // parse UBJSON file
-                std::ifstream f_ubjson(filename + ".ubj", std::ios::binary);
-                std::vector<uint8_t> packed(
-                    (std::istreambuf_iterator<char>(f_ubjson)),
-                    std::istreambuf_iterator<char>());
-                json j2;
-                CHECK_NOTHROW(j2 = json::from_ubjson({packed.data(), packed.size()}));
-
-                // compare parsed JSON values
-                CHECK(j1 == j2);
-            }
-        }
-    }
-}
-*/
-
 TEST_CASE("Universal Binary JSON Specification Examples 1")
 {
     SECTION("Null Value")
@@ -2363,40 +2113,6 @@ TEST_CASE("Universal Binary JSON Specification Examples 1")
     }
 }
 
-/*
-TEST_CASE("Universal Binary JSON Specification Examples 2")
-{
-    for (std::string prefix :
-            {
-                "test/data/universal-binary-json-java/CouchDB4k",
-                "test/data/universal-binary-json-java/MediaContent",
-                "test/data/universal-binary-json-java/TwitterTimeline"
-            })
-    {
-        CAPTURE(prefix);
-
-        // parse JSON file
-        std::ifstream f_json(prefix + ".formatted.json");
-        json j1 = json::parse(f_json);
-
-        SECTION("std::vector<uint8_t>")
-        {
-            // parse UBJSON file
-            std::ifstream f_ubjson(prefix + ".ubj", std::ios::binary);
-            std::vector<uint8_t> packed(
-                (std::istreambuf_iterator<char>(f_ubjson)),
-                std::istreambuf_iterator<char>());
-            json j2;
-            CHECK_NOTHROW(j2 = json::from_ubjson(packed));
-
-            // compare parsed JSON values
-            CHECK(j1 == j2);
-        }
-    }
-}
-*/
-
-
 TEST_CASE("all UBJSON first bytes", "[!throws]")
 {
     // these bytes will fail immediately with exception parse_error.112
diff --git a/test/src/unit-udt.cpp b/test/src/unit-udt.cpp
index 9cfc6e97..040c3e98 100644
--- a/test/src/unit-udt.cpp
+++ b/test/src/unit-udt.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-unicode.cpp b/test/src/unit-unicode.cpp
index 95925dee..568d1d7c 100644
--- a/test/src/unit-unicode.cpp
+++ b/test/src/unit-unicode.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy
diff --git a/test/src/unit-wstring.cpp b/test/src/unit-wstring.cpp
new file mode 100644
index 00000000..a1f4e545
--- /dev/null
+++ b/test/src/unit-wstring.cpp
@@ -0,0 +1,112 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 3.1.2
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
+Copyright (c) 2013-2018 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 <nlohmann/json.hpp>
+
+using nlohmann::json;
+
+bool wstring_is_utf16();
+bool wstring_is_utf16()
+{
+    return (std::wstring(L"💩") == std::wstring(L"\U0001F4A9"));
+}
+
+bool u16string_is_utf16();
+bool u16string_is_utf16()
+{
+    return (std::u16string(u"💩") == std::u16string(u"\U0001F4A9"));
+}
+
+bool u32string_is_utf32();
+bool u32string_is_utf32()
+{
+    return (std::u32string(U"💩") == std::u32string(U"\U0001F4A9"));
+}
+
+TEST_CASE("wide strings")
+{
+    SECTION("std::wstring")
+    {
+        if (wstring_is_utf16())
+        {
+            std::wstring w = L"[12.2,\"Ⴥaäö💤🧢\"]";
+            json j = json::parse(w);
+            CHECK(j.dump() == "[12.2,\"Ⴥaäö💤🧢\"]");
+        }
+    }
+
+    SECTION("invalid std::wstring")
+    {
+        if (wstring_is_utf16())
+        {
+            std::wstring w = L"\"\xDBFF";
+            CHECK_THROWS_AS(json::parse(w), json::parse_error&);
+        }
+    }
+
+    SECTION("std::u16string")
+    {
+        if (u16string_is_utf16())
+        {
+            std::u16string w = u"[12.2,\"Ⴥaäö💤🧢\"]";
+            json j = json::parse(w);
+            CHECK(j.dump() == "[12.2,\"Ⴥaäö💤🧢\"]");
+        }
+    }
+
+    SECTION("invalid std::u16string")
+    {
+        if (wstring_is_utf16())
+        {
+            std::u16string w = u"\"\xDBFF";
+            CHECK_THROWS_AS(json::parse(w), json::parse_error&);
+        }
+    }
+
+    SECTION("std::u32string")
+    {
+        if (u32string_is_utf32())
+        {
+            std::u32string w = U"[12.2,\"Ⴥaäö💤🧢\"]";
+            json j = json::parse(w);
+            CHECK(j.dump() == "[12.2,\"Ⴥaäö💤🧢\"]");
+        }
+    }
+
+    SECTION("invalid std::u32string")
+    {
+        if (u32string_is_utf32())
+        {
+            std::u32string w = U"\"\x110000";
+            CHECK_THROWS_AS(json::parse(w), json::parse_error&);
+        }
+    }
+}
diff --git a/test/src/unit.cpp b/test/src/unit.cpp
index 95659955..6380265b 100644
--- a/test/src/unit.cpp
+++ b/test/src/unit.cpp
@@ -5,6 +5,7 @@
 |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
 Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
 Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
 Permission is hereby  granted, free of charge, to any  person obtaining a copy