registry.register(new ObjectSubscriber());
    assertEquals(2, registry.getSubscribersForTesting(String.class).size());
    assertEquals(1, registry.getSubscribersForTesting(Object.class).size());
  }

  public void testUnregister() {
    StringSubscriber s1 = new StringSubscriber();
    StringSubscriber s2 = new StringSubscriber();

    registry.register(s1);
    registry.register(s2);

    registry.unregister(s1);

    registry.register(new ObjectSubscriber());
    assertEquals(2, registry.getSubscribersForTesting(String.class).size());
    assertEquals(1, registry.getSubscribersForTesting(Object.class).size());
  }

  public void testUnregister() {
    StringSubscriber s1 = new StringSubscriber();
    StringSubscriber s2 = new StringSubscriber();

    registry.register(s1);
    registry.register(s2);

    registry.unregister(s1);

    assertEquals("The dead event must not be re-wrapped.", EVENT, events.get(0).getEvent());
  }

  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);

    assertEquals("The dead event must not be re-wrapped.", EVENT, events.get(0).getEvent());
  }

  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);