@Test
public void invokeNull() {

    FunctionTestUtil.assertResultError(substringBeforeFunction.invoke((String) null, null), InvalidParametersEvent.class);
    FunctionTestUtil.assertResultError(substringBeforeFunction.invoke(null, "test"), InvalidParametersEvent.class);
    FunctionTestUtil.assertResultError(substringBeforeFunction.invoke("test", null), InvalidParametersEvent.class);
}