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

    TransformExecutorService parallel = TransformExecutorServices.parallel(executorService);
    parallel.schedule(first);
    parallel.schedule(second);

    verify(first).run();
    verify(second).run();

    parallel.complete(first);
    parallel.complete(second);
  }