add missing lib

lib/ArduinoJson/test/DynamicJsonBuffer/createObject.cpp

@@ -0,0 +1,22 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("DynamicJsonBuffer::createObject()") {
+  DynamicJsonBuffer json;
+
+  JsonObject &obj = json.createObject();
+  REQUIRE(JSON_OBJECT_SIZE(0) == json.size());
+
+  obj["hello"] = 1;
+  REQUIRE(JSON_OBJECT_SIZE(1) == json.size());
+
+  obj["world"] = 2;
+  REQUIRE(JSON_OBJECT_SIZE(2) == json.size());
+
+  obj["world"] = 3;  // <- same key, should not grow
+  REQUIRE(JSON_OBJECT_SIZE(2) == json.size());
+}