Akka testkit and internal state of underlyingActor

Question

I'm trying to obtain internal state of an actor in my unit test, but by some reason the old state persists.

My actor should be adding/removing/listing self-registering actor services:

class DirectoryServiceActor extends Actor {
  var servicesMap: Map[String, List[ActorRef]] = Map.empty[String, List[ActorRef]]

  def receive = {
    case AddService(serviceType) ⇒
      servicesMap = servicesMap + (serviceType -> (sender :: servicesMap.getOrElse(serviceType, List.empty[ActorRef])))
      sender ! Ack
    case RemoveService ⇒
      val oldMap = servicesMap
      servicesMap = servicesMap.mapValues(list ⇒ (if (list.contains(sender)) list.diff(List(sender)) else list).toList)
      println(servicesMap)
      if (servicesMap.equals(oldMap)) {
        sender ! Nack
      } else {
        sender ! Ack
      }

    case ListServices ⇒
      sender ! services
  }

  def services: Map[String, List[ActorRef]] = this.servicesMap
}

And my test is

"Remove existing service successfully" in {
  implicit val timeout = 10 millis

  val probe = new TestProbe(system)

  val directoryService = TestActorRef[DirectoryServiceActor]
  val actor = directoryService.underlyingActor

  directoryService.tell(AddService("test"), probe.ref)

  probe.expectMsg(timeout, Ack)

  directoryService.tell(RemoveService, probe.ref)

  probe.expectMsg(timeout, Ack)

  println("TEST: " + actor.services)

  actor.services("test") should not contain (probe.ref)
}

Judging by failed test and console output it seems that actor.underlyingActor.services returns the old value:

Map(test -> List())
TEST: Map(test -> List(Actor[akka://myApp/system/testActor3#-2080677614]))

Even though inside of the actor, the variable has already been set to a new value. What have I missed?

Update: Seems not to be related to Akka, actually, but can be worked around using futures in the test:

"Remove existing service successfully" in {
  implicit val timeout = Timeout(100 millis)

  val directoryService = TestActorRef[DirectoryServiceActor]

  val addResponseFuture = directoryService ? AddService(self, "test")

  addResponseFuture.value.get should be(Success(Ack(self)))

  val removeResponseFuture = directoryService ? RemoveService(self)

  removeResponseFuture.value.get should be(Success(Ack(self)))

  val listResponseFuture = directoryService ? ListServices

  listResponseFuture.value.get should be(Success(Map("test" -> List())))

  val actor = directoryService.underlyingActor
  actor.services("test") should not contain (self)

}

I suppose that it is happening due to mapValue not actually creating a new map: Scala: Why mapValues produces a view and is there any stable alternatives?

That seems very odd to me too. Do you see the same behavior if you move the `val actor = directoryService.underlyingActor` line down to just before your `println`? — joescii, Jan 06 '14 at 19:24
What does the actor respond with if you send it a `ListServices` message? — Todd, Jan 06 '14 at 19:57
it returns Map("test" -> List(probe.ref)), even though println(services) inside of case ListServices ⇒ prints Map(test -> List()) — abatyuk, Jan 06 '14 at 20:07
What if you change `println(servicesMap)` in `receive` to `println(services)`? — joescii, Jan 06 '14 at 20:16
added println(services) println(servicesMap) both to RemoveServices and ListServices event handlers - they all print Map(test -> List()) - and at the same probe.expectMsg(timeout, Map("test" -> List())) fails with java.lang.AssertionError: assertion failed: expected Map(test -> List()), found Map(test -> List(Actor[akka://myApp/system/testActor2#-413977955])) — abatyuk, Jan 06 '14 at 20:28

cmbaxter · Accepted Answer · 2014-01-06T22:56:18.107

2

For some reason, I think that mapValues is what's causing issues for you. Try changing the RemoveService handling as follows:

case RemoveService =>
  val oldMap = servicesMap      
  servicesMap = servicesMap.map{
    case (key, list) => (key, list.filterNot(_ == sender))
  }

  if (servicesMap.equals(oldMap)) {
    sender ! Nack
  } else {
    sender ! Ack
  }

edited Jan 06 '14 at 22:56

answered Jan 06 '14 at 22:20

cmbaxter

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And actually found the reason why: http://stackoverflow.com/questions/14882642/scala-why-mapvalues-produces-a-view-and-is-there-any-stable-alternatives – abatyuk Jan 07 '14 at 02:44

Akka testkit and internal state of underlyingActor

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