assertTrue(listenableFuture.isDone());
  }

  /** A Future that doesn't implement ListenableFuture, useful for testing listenInPoolThread. */
  private static final class NonListenableSettableFuture<V> extends ForwardingFuture<V> {
    static <V> NonListenableSettableFuture<V> create() {
      return new NonListenableSettableFuture<V>();
    }

    final SettableFuture<V> delegate = SettableFuture.create();

    @Override

    assertTrue(listenableFuture.isDone());
  }

  /** A Future that doesn't implement ListenableFuture, useful for testing listenInPoolThread. */
  private static final class NonListenableSettableFuture<V> extends ForwardingFuture<V> {
    static <V> NonListenableSettableFuture<V> create() {
      return new NonListenableSettableFuture<V>();
    }

    final SettableFuture<V> delegate = SettableFuture.create();

    @Override

                return new ThrowingScheduledFuture<>();
              }
            },
            testRunnable);
    assertTrue(called);
  }

  private static final class ThrowingScheduledFuture<V> extends ForwardingFuture<V>
      implements ScheduledFuture<V> {
    @Override
    protected Future<V> delegate() {
      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override

                return new ThrowingScheduledFuture<>();
              }
            },
            testRunnable);
    assertTrue(called);
  }

  private static final class ThrowingScheduledFuture<V> extends ForwardingFuture<V>
      implements ScheduledFuture<V> {
    @Override
    protected Future<V> delegate() {
      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override