ServiceManager serviceManager = new ServiceManager(asList(a, b));
    serviceManager.startAsync().awaitHealthy();
    ImmutableMap<Service, Duration> startupTimes = serviceManager.startupDurations();
    assertThat(startupTimes).hasSize(2);
    assertThat(startupTimes.get(a)).isAtLeast(Duration.ofMillis(150));
    assertThat(startupTimes.get(b)).isAtLeast(Duration.ofMillis(353));
  }

  @SuppressWarnings("Java7ApiChecker")
  // If users use this when they shouldn't, we hope that NewApi will catch subsequent Duration calls
  @IgnoreJRERequirement
  public ImmutableMap<Service, Duration> startupDurations() {
    return ImmutableMap.copyOf(
        Maps.<Service, Long, Duration>transformValues(startupTimes(), Duration::ofMillis));
  }

  @Override
  public String toString() {

   *     by startup time.
   * @since 31.0 (but only since 33.4.0 in the Android flavor)
   */
  @J2ObjCIncompatible
  public ImmutableMap<Service, Duration> startupDurations() {
    return ImmutableMap.copyOf(
        Maps.<Service, Long, Duration>transformValues(startupTimes(), Duration::ofMillis));
  }

  @Override
  public String toString() {