/**
   * Subscriber that synchronizes invocations of a method to ensure that only one thread may enter
   * the method at a time.
   */
  @VisibleForTesting
  static final class SynchronizedSubscriber extends Subscriber {

    private SynchronizedSubscriber(EventBus bus, Object target, Method method) {
      super(bus, target, method);
    }

    @Override

    assertThat(s1).isInstanceOf(Subscriber.SynchronizedSubscriber.class);

    // a thread-safe method should not create a synchronized subscriber
    Subscriber s2 = Subscriber.create(bus, this, getTestSubscriberMethod("threadSafeMethod"));
    assertThat(s2).isNotInstanceOf(Subscriber.SynchronizedSubscriber.class);
  }

  public void testInvokeSubscriberMethod_basicMethodCall() throws Throwable {