public static TransformExecutorService parallel(ExecutorService executor) {
    return new ParallelTransformExecutor(executor);
  }
@Test
  public void parallelRejectedStillActiveThrows() {
    @SuppressWarnings("unchecked")
    DirectTransformExecutor<Object> first = mock(DirectTransformExecutor.class);

    TransformExecutorService parallel = TransformExecutorServices.parallel(executorService);
    executorService.shutdown();
    thrown.expect(IllegalStateException.class);
    thrown.expectMessage("still active");
    parallel.schedule(first);
  }