manager.addListener(listener, directExecutor());
    assertState(manager, Service.State.NEW, a, b);
    assertFalse(manager.isHealthy());
    manager.startAsync().awaitHealthy();
    assertState(manager, Service.State.RUNNING, a, b);
    assertTrue(manager.isHealthy());
    assertTrue(listener.healthyCalled);
    assertFalse(listener.stoppedCalled);
    assertTrue(listener.failedServices.isEmpty());

    manager.addListener(listener, directExecutor());
    assertState(manager, Service.State.NEW, a, b);
    assertFalse(manager.isHealthy());
    manager.startAsync().awaitHealthy();
    assertState(manager, Service.State.RUNNING, a, b);
    assertTrue(manager.isHealthy());
    assertTrue(listener.healthyCalled);
    assertFalse(listener.stoppedCalled);
    assertTrue(listener.failedServices.isEmpty());

  /**
   * Waits for the {@link ServiceManager} to become {@linkplain #isHealthy() healthy}. The manager
   * will become healthy after all the component services have reached the {@linkplain State#RUNNING
   * running} state.
   *
   * @throws IllegalStateException if the service manager reaches a state from which it cannot
   *     become {@linkplain #isHealthy() healthy}.
   */
  public void awaitHealthy() {
    state.awaitHealthy();