@Test
public void invokeYear() {

    FunctionTestUtil.assertResult(yamFunction.invoke(Year.of(2017), Year.of(2020)), ComparablePeriod.of(3, 0, 0));
    FunctionTestUtil.assertResult(yamFunction.invoke(Year.of(2017), Year.of(2014)), ComparablePeriod.of(-3, 0, 0));
}