List<Future<String>> results;

    results = service.invokeAll(callables);
    assertThat(getOnlyElement(results)).isInstanceOf(TrustedListenableFutureTask.class);

    results = service.invokeAll(callables, 1, SECONDS);
    assertThat(getOnlyElement(results)).isInstanceOf(TrustedListenableFutureTask.class);

    /*
     * TODO(cpovirk): move ForwardingTestCase somewhere common, and use it to

    List<Future<String>> results;

    results = service.invokeAll(callables);
    assertThat(getOnlyElement(results)).isInstanceOf(TrustedListenableFutureTask.class);

    results = service.invokeAll(callables, 1, SECONDS);
    assertThat(getOnlyElement(results)).isInstanceOf(TrustedListenableFutureTask.class);

    /*
     * TODO(cpovirk): move ForwardingTestCase somewhere common, and use it to

   * @throws IllegalArgumentException if the iterable contains multiple elements
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getOnlyElement(Iterable<T> iterable) {
    return Iterators.getOnlyElement(iterable.iterator());
  }

  /**
   * Returns the single element contained in {@code iterable}, or {@code defaultValue} if the
   * iterable is empty.
   *

      assertThat(future.isDone()).isTrue();
      // inspect state and ensure it is correct!
      // asserts that all get calling threads received the same value
      Object result = Iterables.getOnlyElement(finalResults);
      if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        if (future.wasInterrupted()) {

      assertThat(future.isDone()).isTrue();
      // inspect state and ensure it is correct!
      // asserts that all get calling threads received the same value
      Object result = Iterables.getOnlyElement(finalResults);
      if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        if (future.wasInterrupted()) {