public static AfterProcessingTimeStateMachine pastFirstElementInPane() {
    return new AfterProcessingTimeStateMachine(IDENTITY);
  }
@Test
  public void testClear() throws Exception {
    SimpleTriggerStateMachineTester<IntervalWindow> tester =
        TriggerStateMachineTester.forTrigger(
            AfterProcessingTimeStateMachine.pastFirstElementInPane()
                .plusDelayOf(Duration.millis(5)),
            FixedWindows.of(Duration.millis(10)));

    tester.injectElements(1, 2, 3);
    IntervalWindow window = new IntervalWindow(new Instant(0), new Instant(10));
    tester.clearState(window);
    tester.assertCleared(window);
  }