I've blogged previously about testing messages sent back to the sender and to a child actor. The final common scenario I come across is testing actors that send a messages back to its supervisor/parent. If it is in response to a message from the parent you can use the same technique as described in testing messages sent back to the sender.

However, if that is not the case then TestKit has a very simple way you can do it with the TestActorRef and a TestProbe. Any where you have a piece of code that looks like this:

context.parent ! "Any message"

For example:

Then you can test it by passing a TestProbe to your TestActorRef and using the expect* functions on the TestProbe. So to test the actor above your test will look something like this:

As you can see the TestActorRef can take an ActorRef to use as a parent when you use the apply method that takes in a Props.

Full code here. Happy testing.