}

  public void testMissingSubscribe() {
    bus.register(new Object());
  }

  public void testUnregister() {
    StringCatcher catcher1 = new StringCatcher();
    StringCatcher catcher2 = new StringCatcher();
    assertThrows(IllegalArgumentException.class, () -> bus.unregister(catcher1));

    bus.register(catcher1);
    bus.post(EVENT);
    bus.register(catcher2);

  }

  public void testMissingSubscribe() {
    bus.register(new Object());
  }

  public void testUnregister() {
    StringCatcher catcher1 = new StringCatcher();
    StringCatcher catcher2 = new StringCatcher();
    assertThrows(IllegalArgumentException.class, () -> bus.unregister(catcher1));

    bus.register(catcher1);
    bus.post(EVENT);
    bus.register(catcher2);

  protected void setUp() throws Exception {
    super.setUp();
    executor = new FakeExecutor();
    bus = new AsyncEventBus(executor);
  }

  public void testBasicDistribution() {
    StringCatcher catcher = new StringCatcher();
    bus.register(catcher);

    // We post the event, but our Executor will not deliver it until instructed.
    bus.post(EVENT);

    List<String> events = catcher.getEvents();