}

  /**
   * Gets an iterator representing an immutable snapshot of all subscribers to the given event at
   * the time this method is called.
   */
  Iterator<Subscriber> getSubscribers(Object event) {
    ImmutableSet<Class<?>> eventTypes = flattenHierarchy(event.getClass());

    List<Iterator<Subscriber>> subscriberIterators =
        Lists.newArrayListWithCapacity(eventTypes.size());

   * already a {@link DeadEvent}, it will be wrapped in a DeadEvent and reposted.
   *
   * @param event event to post.
   */
  public void post(Object event) {
    Iterator<Subscriber> eventSubscribers = subscribers.getSubscribers(event);
    if (eventSubscribers.hasNext()) {
      dispatcher.dispatch(event, eventSubscribers);
    } else if (!(event instanceof DeadEvent)) {
      // the event had no subscribers and was not itself a DeadEvent

    assertEquals("Event should be available.", EVENT, handler.context.getEvent());
    assertEquals("Subscriber should be available.", subscriber, handler.context.getSubscriber());
    assertEquals(
        "Method should be available.",
        subscriber.getClass().getMethod("throwExceptionOn", String.class),
        handler.context.getSubscriberMethod());
  }

    assertEquals("Event should be available.", EVENT, handler.context.getEvent());
    assertEquals("Subscriber should be available.", subscriber, handler.context.getSubscriber());
    assertEquals(
        "Method should be available.",
        subscriber.getClass().getMethod("throwExceptionOn", String.class),
        handler.context.getSubscriberMethod());
  }