Test: extracted executable Cpp11Tests

extras/tests/Cpp11/use_long_long_1.cpp

@@ -0,0 +1,17 @@
+#define ARDUINOJSON_USE_LONG_LONG 1
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+
+TEST_CASE("ARDUINOJSON_USE_LONG_LONG == 1") {
+  DynamicJsonDocument doc(4096);
+  JsonObject root = doc.to<JsonObject>();
+
+  root["A"] = 123456789123456789;
+  root["B"] = 987654321987654321;
+
+  std::string json;
+  serializeJson(doc, json);
+
+  REQUIRE(json == "{\"A\":123456789123456789,\"B\":987654321987654321}");
+}