*/
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  @IgnoreJRERequirement // Users will use this only if they're already using Duration.
  public static void sleepUninterruptibly(Duration sleepFor) {
    sleepUninterruptibly(toNanosSaturated(sleepFor), TimeUnit.NANOSECONDS);
  }

  // TODO(user): Support Sleeper somehow (wrapper or interface method)?

        @Override
        public void run() {
          Uninterruptibles.sleepUninterruptibly(delay, MILLISECONDS);
          notifyStarted();
        }
      }.start();
    }

    @Override
    protected void doStop() {
      new Thread() {
        @Override
        public void run() {
          Uninterruptibles.sleepUninterruptibly(delay, MILLISECONDS);
          notifyStopped();
        }
      }.start();

    @Override
    protected void doAction() {}
  }

  private static void sleepSuccessfully(long sleepMillis) {
    Completion completed = new Completion(sleepMillis - SLEEP_SLACK);
    Uninterruptibles.sleepUninterruptibly(sleepMillis, MILLISECONDS);
    completed.assertCompletionExpected();
  }

  private static void assertTimeNotPassed(Stopwatch stopwatch, long timelimitMillis) {