@Test
public void invokeDurationHours() {

    FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofHours(9)), "PT9H");
    FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofHours(200)), "P8DT8H");
    FunctionTestUtil.assertResult(stringFunction.invoke(Duration.ofHours(-200)), "-P8DT8H");
}