How to test that akka actor message was sent to it's child

Question

I have ParentActor and ChildActor as follows:

class ParentActor extends UntypedActor {
    final ActorSystem system = ActorSystem.create("MySystem");

    final ActorRef child = system.actorOf(Props.create(ChildActor.class), "child")

    @Override
    void onReceive(Object message) throws Exception {
        if (message instanceof String) {
            getContext().watch(child)
            child.tell(message, getSelf())
        } else {
            unhandled(message)
        }
    }
}

class ChildActor extends UntypedActor {
    @Override
    void onReceive(Object message) throws Exception {
        if (message instanceof String) {
            context().parent().tell("Hello from child actor!", self());
        }
    }
}    

I want to test the relationship between parent and child (If I send String message to ParentActor assure that child has got it) using TestKit and in java. Can you help me with this?

Answer 1

Change your parent - inject Child actor Props via constructor. And change your Child - inject parent reference via constructor. In test when creating Parent inject another Child Props which accepts test actor as a parameter. Change:

context().parent().tell("Hello from child actor!", self());

to

parentField.tell("Hello from child actor!", self());

Then in your test use akka test actor instead of Parent and pass it to Child. And you can check response via expectMsgEquals method.