Question

I have a process that runs in a thread (used as a realtime signal analysis process). I want to feed that thread process a known input, and then test — in jUnit — that the output is correct. I have a callback listener that can notify me when the thread finishes processing the data and I can run assertions on the result successfully by registering the test case itself as a listener.
When those assertions fail, they do throw an exception. But that exception is not registered as a failure by jUnit, presumably because they are happening outside of a test method.

How do I structure my jUnit test so that the test fails correctly after the listener returns? Here’s a simplified version of the code.

 public class PitchDetectionTest extends TestCase 
    implements EngineRunCompleteListener() {
  AudioData            fixtureData;
  PitchDetectionEngine pitchEngine;

  public void setUp() {
    fixtureData = <stuff to load audio data>;
  }

  public void testCorrectPitch() {
    pitchEngine = new PitchEngine(fixtureData);
    pitchEngine.setCompletionListener(this);
    pitchEngine.start();   
    // delay termination long enough for the engine to complete
    try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); }
  }

  // gets called by the PitchEngine when it has finished processing all data in the
  // fixtureData.   This is the only method defined by interface    
  // EngineRunCompleteListener.
  public void notifyEngineRunComplete() {

    // The real code asserts things about the PitchEngine's results.   When they fail, 
    // an exception is thrown that I can see in the console, but this unit test still  
    // shows as 'success' in the jUnit interface.   What I want is to see 
    // testCorrectPitch() fail.
    assertTrue(false);  

  }

}

public class PitchEngine () {
  EngineRunCompleteListener completionListener();
  Thread myThread;

  public void start() {
    // other stuff
    myThread = new Thread(this);
    myThread.start();    
  }

  public void run() {
    while (some condition) {
      // do stuff with the data
    }
    if (engineRunCompleteListener != null) {
      engineRunCompleteListener.notifyEngineRunComplete();
    }
  }

}

Answer 1

You already have two threads running. Your junit thread, and the process thread (started by myThread.start().
Off the top of my head, I can think of at least two options that you have, all of them involving moving the assertion away from notifyEngineRunComplete. For example:

• You can use join to wait for the process thread to finish, and then do your assertions (Javadoc here).
• You can put your junit thread to sleep by waiting on a monitor object, and then in your callback function notify this monitor. This way you’ll know that the process has finished.
• You can use an Executor and a Future object. I think this would be the coolest solution if it works with your classes (Javadoc here).