How do I write a JUnit test case to test threads and events

Question

I have a java code which works in one (main) thread. From the main thread, i spawn a new thread in which I make a server call. After the server call is done, I am doing some

Answer 1

When your only problem is waiting for the result, use ExecutorService for spawning your threads. It can accept work jobs both as Runnable and Callable. When you use the latter, then you are given a Future object in return, that can be used to wait for the result. You should consider using ExecutorService anyway, as from what I understand, you create many threads, and this is a perfect use case for executor services.

class AnyClass {
    private ExecutorService threadPool = Executors.newFixedThreadPool(5);

    public List> anyMethod() {
        List futures = new ArrayList<>();

        futures.add(threadPool.submit(() -> {
            // Do your job here
            return anyStatusCode;
        }));

        futures.add(threadPool.submit(() -> {
            // Do your other job here
            return anyStatusCode;
        }));

        return futures;
    }
}

And the test class:

class TestAnyClass {
    @Test
    public void testAnyMethod() {
        AnyClass anyObject = new AnyClass();

        List> futures = anyObject.anyMethod();
        CompletableFuture[] completable = futures.toArray(new CompletableFuture[futures.size()]);

        // Wait for all
        CompletableFuture.allOf(completable).join();
    }
}