@Override
  public Throwable getError() {
    return _delegate.getError();
  }
@Test
  public void testGetError() {
    final Promise<String> delegate = Promises.error(new Exception());
    final Promise<String> promise = new DelegatingPromise<String>(delegate);
    assertEquals(delegate.getError(), promise.getError());
    assertEquals(delegate.isDone(), promise.isDone());
    assertEquals(delegate.isFailed(), promise.isFailed());
  }