Test size() after calling CreateObject

tests/StaticJsonBufferTests.cpp

@@ -11,4 +11,15 @@ TEST(StaticJsonBuffer, InitialSizeIsZero)
 {
     StaticJsonBuffer<42> json;
     EXPECT_EQ(0, json.size());
+}
+
+TEST(StaticJsonBuffer, WhenCreateObjectIsCalled_ThenSizeIsIncreasedByOne)
+{
+    StaticJsonBuffer<42> json;
+
+    json.createObject();
+    EXPECT_EQ(1, json.size());
+    
+    json.createObject();
+    EXPECT_EQ(2, json.size());
 }