@VisibleForTesting
  static class Application {

    final ExecutorService getExitingExecutorService(
        ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {
      useDaemonThreadFactory(executor);
      ExecutorService service = unconfigurableExecutorService(executor);
      addDelayedShutdownHook(executor, terminationTimeout, timeUnit);
      return service;
    }