Service a = new NoOpDelayedService(50);
    ServiceManager manager = new ServiceManager(asList(a));
    manager.startAsync();
    assertThrows(TimeoutException.class, () -> manager.awaitHealthy(1, TimeUnit.MILLISECONDS));
    manager.awaitHealthy(5, SECONDS); // no exception thrown

    manager.stopAsync();
    assertThrows(TimeoutException.class, () -> manager.awaitStopped(1, TimeUnit.MILLISECONDS));

    Service a = new NoOpDelayedService(50);
    ServiceManager manager = new ServiceManager(asList(a));
    manager.startAsync();
    assertThrows(TimeoutException.class, () -> manager.awaitHealthy(1, TimeUnit.MILLISECONDS));
    manager.awaitHealthy(5, SECONDS); // no exception thrown

    manager.stopAsync();
    assertThrows(TimeoutException.class, () -> manager.awaitStopped(1, TimeUnit.MILLISECONDS));

   * running} state.
   *
   * @throws IllegalStateException if the service manager reaches a state from which it cannot
   *     become {@linkplain #isHealthy() healthy}.
   */
  public void awaitHealthy() {
    state.awaitHealthy();
  }

  /**
   * Waits for the {@link ServiceManager} to become {@linkplain #isHealthy() healthy} for no more