How do we test Actors in Java?

Question

The only thing I've seen so far is someone posting an example of testing a TypedActor. I take it there's no way of testing an UntypedActor through say Junit? Akka docs are getting better by the day, but I don't see testing mentioned. Is it really obvious and I'm just missing something?

Answer 1

For testing with JUnit you'll need to use the facilities provided by JUnit, the docs on testing Actor (Java equiv is UntypedActor) is here: http://akka.io/docs/akka/snapshot/scala/testing.html

Answer 2

It is possible, at least with version 1.3 and 2.0 and the akka-testkit library.

You do something like this to setup your actor:

@Before
public void initActor() {
    actorSystem = ActorSystem.apply();
    actorRef = TestActorRef.apply(new AbstractFunction0() {

        @Override
        public Pi.Worker apply() {
            return new Pi.Worker();
        }

    }, actorSystem);
}

You can then use the TestProbe class to test your actor (for version 1.3 it is slightly different):

@Test
public void calculatePiFor0() {
    TestProbe testProbe = TestProbe.apply(actorSystem);
    Pi.Work work = new Pi.Work(0, 0);        
    actorRef.tell(work, testProbe.ref());

    testProbe.expectMsgClass(Pi.Result.class);     
    TestActor.Message message = testProbe.lastMessage();
    Pi.Result resultMsg = (Pi.Result) message.msg();
    assertEquals(0.0, resultMsg.getValue(), 0.0000000001);
}

There is more available in a blogpost I wrote on some of my experiences: http://fhopf.blogspot.com/2012/03/testing-akka-actors-from-java.html

Answer 3

You might be interested in a blog post I've wrote: Testing AKKA actors with Mockito and FEST-Reflect The example I'm using is based on JUnit, Mockito, and FEST-Reflect. Let me know if that is useful to you.