}

  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);