public FEELFnResult<String> invoke(@ParameterName("string") String string, @ParameterName("start position") Number start) {
        return invoke(string, start, null);
    }
@Test
    void invokeNull3ParamsMethod() {
        FunctionTestUtil.assertResultError(substringFunction.invoke(null, null, null), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", null, null), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke("test", null, 2), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke(null, 0, null), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke(null, null, 2), InvalidParametersEvent.class);
        FunctionTestUtil.assertResultError(substringFunction.invoke(null, 0, 2), InvalidParametersEvent.class);
    }