Unit Testing Bolts Tasks With Continuations (Android)

Question

I'm trying to write some tests for an Android application where we are integrating Bolts.

The object under test works by creating a Task and executing it in the background:

Task<MyResult> currentTask;

currentTask = MyTaskFactory.getImportantTask(parameters ...);

currentTask.continueWith(new Continuation<MyResult,MyResult>() {
        @Override
        public MyResult then(Task<MyResult> task) throws Exception {
            MyResult result = task.getResult();

            if (!task.isFaulted()) {
                if (DEBUG) {
                    logger.v("got login result back: " + result.toString());
                }

                if (result.getSuccess()) {
                    callback.onMySuccess(result.getData());
                } else {
                    callback.onMyError(result.getStatusCode(), result.getError());
                }
           }

            return result;
        }
    }, Task.UI_THREAD_EXECUTOR);

MyTaskFactory.getImportantTask() returns a Task, and my object under test gets this task and executes it in the background. When it completes, the completion should get executed.

I have verified that in the actual app, this code is working correctly. My problem arises because I am trying to run this under Robolectric/Mockito.

Here is the code under test:

myobject.runTaskWithContinuation(parameters...);

ShadowLog.d(TAG, "Waiting....");

Task<AuthenticationResult> task = controller.getCurrentTask();

assert(task != null);

ShadowApplication.runBackgroundTasks();
ShadowLooper.runUiThreadTasksIncludingDelayedTasks();

ShadowLog.d(TAG, "Finished!");

Using this code, and by mocking and instrumenting the calls made by the Task and the Continuation, I have verified that the Task is executing and generating a result, yet the Continuation never gets called. If I wait for the Task to complete, my unit test will never finish.

I am certain that I am doing something wrong here, but I really don't know what. How can I make sure that the Continuation gets called under test?

Answer 1

In your unit tests, since you have access to the Task directly, call

task.waitForCompletion()

For example:

@Test
public void directTaskAccess() throws InterruptedException {
    Task<Boolean> task = doWorkTask();
    task.waitForCompletion();
    assertTrue(task.getResult());
}

public Task<Boolean> doWorkTask() {
    return Task.callInBackground(() -> {

        // simulate doing 'hard' work
        Thread.sleep(1000);
        return true;
    });
}

For other tests when you don't have access to the Task reference, you might need to do a little extra work.

This blog post details more about it: Unit Testing Asynchronous Bolts Tasks

Answer 2

Use a CountDownLatch to make the Test thread to wait until your Continuation has been reached

here's a sample code that runs on my Robolectric test:

@Test
public void test1() throws Throwable {
    success = false;
    final CountDownLatch signal = new CountDownLatch(1);
    task.onSuccess(new Continuation<Object, Object>() {
        @Override
        public Object then(Task<Object> task) throws Exception {
            if (condition == true) {
                success = true;
            }
            signal.countDown();
            return null;
        }
    });
    signal.await(30, TimeUnit.SECONDS);
    assertTrue(success);
}