@Test
public void invokeContextNonEmpty() {

    final Map<String, Object> childContextMap = new HashMap<>();
    childContextMap.put("childKey1", "childValue1");
    final Map<String, Object> contextMap = new HashMap<>();
    contextMap.put("key1", "value1");
    contextMap.put("key2", childContextMap);
    FunctionTestUtil.assertResult(stringFunction.invoke(contextMap), "{ key1 : value1, key2 : { childKey1 : childValue1 } }");
}