List<? extends Future<?>> unused = executor.invokeAll(tasks);
  }

  public void testListeningDecorator() throws Exception {
    ListeningExecutorService service = listeningDecorator(newDirectExecutorService());
    assertSame(service, listeningDecorator(service));
    List<Callable<String>> callables = ImmutableList.of(Callables.returning("x"));
    List<Future<String>> results;

    results = service.invokeAll(callables);

    List<? extends Future<?>> unused = executor.invokeAll(tasks);
  }

  public void testListeningDecorator() throws Exception {
    ListeningExecutorService service = listeningDecorator(newDirectExecutorService());
    assertSame(service, listeningDecorator(service));
    List<Callable<String>> callables = ImmutableList.of(Callables.returning("x"));
    List<Future<String>> results;

    results = service.invokeAll(callables);

  @GwtIncompatible // TODO
  public static ListeningExecutorService listeningDecorator(ExecutorService delegate) {
    return (delegate instanceof ListeningExecutorService)
        ? (ListeningExecutorService) delegate
        : (delegate instanceof ScheduledExecutorService)
            ? new ScheduledListeningDecorator((ScheduledExecutorService) delegate)
            : new ListeningDecorator(delegate);
  }

  /**