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);