Thread thread = new Thread(() -> { /code } and Executorservice.submit(thread). How to write junit on this using powermock

Question

Please help me write Junit for this piece of code using Mockito /Powermock, Finding it difficult due to lamda expression and executor service.

public class myClass {

    ExecutorService executorService;

    public void testMethod(String a){
        Thread thread = new Thread(() -> {
            //logic
            a= testDAo.getStatus();
            while (true) {
                if (Thread.interrupted()) {
                    break;
                }

                if (a() != "done" || a() != "fail") {
                    Thread.yield();
                    try {
                        Thread.sleep(10000);
                    } catch (InterruptedException e) {
                    }
                } else {
                    break;
                }
            }
        }
        Future task = executorService.submit(thread);

        while (!task.isDone()) {
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
            }
        }
    }

}

GhostCat · Answer 1 · 2017-12-05T13:43:05.110

Various things here:

first of all: for testing executors and parallel execution, using a same thread executor can be extremely helpful (because it takes out the parallel aspect)
you have difficulties writing a unit test - because your production code is way too complicated.

Thus the real answer is: step back and improve your production code. Why again are you pushing a thread into an executor service?

The executor service is already doing things on a thread pool (at least that is how you normally use them). So you push a thread into a thread pool, and then you have code that waits "two" times (first within that thread, and then outside on the future). That just adds a ton of complexity for small gain.

Long story short:

I would get rid of that "inner thread" - just have the executor task wait until the result becomes available
Then: if lambda's give you trouble - then don't use them. Just create a named small class that implements that code. And then you can write unit tests for that small class. In other words: don't create huge "units" that do 5 different things. The essence of a good unit is to one thing (single responsibility principle!). And as soon as you follow that idea testing becomes much easier, too.

Thanks for your input. I could get this working using the below code. We let the actual thread execute and I mocked all the logic inside the thread using Mockito and Powermock.Spy @SpyExecutorService executorService= Executors.newFixedThreadPool(2); — Ram Babu, Dec 06 '17 at 06:26
My honest opinion: wrong approach. You kept your **hard to test** complicated production code - and you worked around the symptoms by using PowerMock. That is exactly why I find PowerMock to be a bad choice. Because it encourages people to keep their bad design ... — GhostCat, Dec 06 '17 at 07:37

Thread thread = new Thread(() -> { /code } and Executorservice.submit(thread). How to write junit on this using powermock

1 Answers1