Logging all messages sent to an Akka TestKit TestProbe

I'm trying to log all messages received by a TestKit TestProbe, which is proving to be somewhat difficult. I'm aware of the Actor Logging section in the docs where it says one should use the debug.receive option in combination with a LogginReceive block. This however doesn't work when I'm not in control of the actor's implementation.

The only idea I had was subclassing akka.testkit.TestActor to use a LoggingReceive and then subclass TestKit to make it create instances of my TestActor subclass instead, but that didn't work because most functionality there is private to the akka namespace (and for good reason, I suppose).

Sorry, got your question a little wrong at first, so here is my approach.

Create a wrapper actor, that logs the messages:

class LoggingActor(fac: => Actor) extends Actor {

  val underlying = context.system.actorOf(Props(fac))

  def receive = {
    LoggingReceive {
      case x ⇒ underlying.tell(x, sender)
    }
  }
}

and then just create your TestActorRef with your actor wrapped in the LoggingActor:

  val echo = TestActorRef(new LoggingActor(new FooActor))

  echo ! "hello world"