@Test
public void invokeAppendSomething() {

    FunctionTestUtil.assertResultList(appendFunction.invoke(Collections.emptyList(), new Object[]{"test"}), Arrays.asList("test"));
    FunctionTestUtil.assertResultList(appendFunction.invoke(Arrays.asList("test"), new Object[]{"test2"}), Arrays.asList("test", "test2"));
    FunctionTestUtil.assertResultList(appendFunction.invoke(Arrays.asList("test"), new Object[]{"test2", "test3"}), Arrays.asList("test", "test2", "test3"));
}