🚧 toward an ordered_json type

test/CMakeLists.txt

@@ -123,6 +123,7 @@ set(files
     src/unit-modifiers.cpp
     src/unit-msgpack.cpp
     src/unit-noexcept.cpp
+    src/unit-ordered_json.cpp
     src/unit-pointer_access.cpp
     src/unit-readme.cpp
     src/unit-reference_access.cpp

test/src/unit-ordered_json.cpp

@@ -0,0 +1,61 @@
+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 3.8.0
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
+Copyright (c) 2013-2019 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 "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+using nlohmann::json;
+using nlohmann::ordered_json;
+
+
+TEST_CASE("ordered_json")
+{
+    json j;
+    ordered_json oj;
+
+    j["element3"] = 3;
+    j["element1"] = 1;
+    j["element2"] = 2;
+
+    oj["element3"] = 3;
+    oj["element1"] = 1;
+    oj["element2"] = 2;
+
+    CHECK(j.dump() == "{\"element1\":1,\"element2\":2,\"element3\":3}");
+    CHECK(oj.dump() == "{\"element3\":3,\"element1\":1,\"element2\":2}");
+
+    CHECK(j == json(oj));
+    CHECK(ordered_json(json(oj)) == ordered_json(j));
+
+    j.erase("element1");
+    oj.erase("element1");
+
+    CHECK(j.dump() == "{\"element2\":2,\"element3\":3}");
+    CHECK(oj.dump() == "{\"element3\":3,\"element2\":2}");
+}