Scheduling a response callback

I have an Android service which must offload a task to a different thread but schedule the response callback unto the calling thread. After much thinking I came up with this code:

```
public void testRequestingAScheduleUpdateShouldNotBlockAndDeliverItOnTheCallingThread() throws Exception {
final StreamSchedule mockSchedule = new StreamSchedule(
new StreamMetadata("TyPhone", "Tidal Waves 028"),
new StreamMetadata[] { new StreamMetadata(null, "The Progmatic Radio Show 002 with Ashley Bonsall") },
new StreamMetadata[] { new StreamMetadata("TEKNO", "Sound Escalation 065 with Xabi") }
);

final boolean[] threadBlocked = {true};
LooperThread looperThread = new LooperThread();
looperThread.start();

StreamScheduleProvider mockScheduleProvider = mock(StreamScheduleProvider.class);
when(mockScheduleProvider.getCurrentStreamSchedule()).then(invocation -> {
threadBlocked[0] = Thread.currentThread().getId() == looperThread.getId();
return mockSchedule;
});
DataAccessModule.scheduleProviderOverride = mockScheduleProvider;

final long[] callingThreadId = {-1};

ScheduleUpdateListener updateListener = mock(ScheduleUpdateListener.class);
doAnswer(invocation -> {
callingThreadId[0] = Thread.currentThread().getId();
looperThread.stopLooper();
return null;
}).when(updateListener).onScheduleChanged(any(StreamSchedule.class));

PlaybackServiceBinder serviceBinder = (PlaybackServiceBinder) bindService(getServiceIntent());
serviceBinder.subscribeScheduleUpdates(updateListener);
looperThread.getHandler().post(serviceBinder::updateSchedule);
looperThread.join();

verify(updateListener).onScheduleChanged(mockSchedule);
assertFalse("The thread was blocked, this is unacceptable", threadBlocked[0]);
assertEquals("The update callback was not called on the requesting thread", callingThreadId[0], looperThread.getId());
}

class LooperThread extends Thread

Disclaimer: I don't know Android. I've wrote two or three programs for it.

Also, I don't have your full code so can't be sure about some of the classes this code relies on.

• Test name has an "and", seems like two tests?

• Test throws Exception, do you have tests for that?

• You don't need to start test name with tests, unless you use JUnit 3.

• When LooperThread runs, it calls Looper.prepare() and Looper.loop(). What these do?

• LooperThread extends Thread, why not implement Runnable? You only implement run() then?

• Further reinforcement to point 1) - you have more than one assertion. If verify buckles, other assertions aren't tested. Is that fine?

• Why do you need a final boolean[] threadBlocked = {true}; over just a final boolean? I found no other reference than to that one element, via threadBlocked[0]?

• Is this test alone it it's class? If so, I'd extract mocking out of it. Readability / clarity / easier to spot things.

• Have you tried structuring the test into classic given - when - then or assess - act - assert?

StackExchange Code Review Q#88420, answer score: 2