Testing Akka PubSub mediator with specs2 - scala

Question

I'm fairly new to testing Akka and have been stuck trying to simply verify that a message is sent to a subscriber when a publish message is sent to an Akka mediator from akka.contrib.pattern.DistributedPubSubMediator. I'd like to understand how to get his working before I branch into verifying actual business logic.
import akka.actor.{ ActorRef, Actor }
import akka.contrib.pattern.DistributedPubSubExtension
import akka.contrib.pattern.DistributedPubSubMediator.{ Subscribe, Publish }
import akka.testkit.{ ImplicitSender, TestKit }
import org.specs2.mutable.{ After, Specification }
import queues.{ Publisher, Subscriber }
import scala.concurrent.duration._
class PubSubActorSupport extends TestKit(ActorSystem("PubSubTest")) with ImplicitSender with After {
override def after = system.shutdown()
lazy val subscriberRef = system.actorOf(Props(classOf[Subscriber]))
lazy val publisherRef = system.actorOf(Props(classOf[Publisher]))
lazy val testActorRef = system.actorOf(Props(classOf[MyTestActor]))
}
class MyTestActor extends Actor {
def receive: Receive = { case x => () }
}
object EventsTest extends Specification {
"Publish/Subscriber Actors" should {
"work" in new PubSubActorSupport {
subscriberRef ! ("topic", testActorRef)
publisherRef ! ("topic", "Hello!")
// assert that MyTestActor received "Hello!" from the publisher actor
expectMsg(500 milli, "Hello!")
}
}
}
I figure I'm not using expectMsg correctly. My Subscriber/Publisher actors are below.
trait Mediator extends Actor {
val mediator = DistributedPubSubExtension(context.system).mediator
}
class Publisher extends Mediator {
def receive = {
case (topic: String, msg: Any) => mediator ! Publish(topic, msg)
}
}
class Subscriber extends Mediator {
def receive = {
case (topic: String, ref: ActorRef) => mediator ! Subscribe(topic, ref)
}
}

Answer 1

Check this sample for testing SubPub pattern
https://github.com/JAVEO/clustered-chat/blob/master/test/actors/UserSocketSpec.scala
expectMsg just verify message that is send to "sender". And if you want to verify a message sent to a subscribers, write like this (From the sample above)
val mediator = DistributedPubSubExtension(system).mediator
val chatMember1 = TestProbe()
mediator ! Subscribe(topic, chatMember1.ref)
//... Call the publisher to publish message
chatMember1.expectMsg(ChatMessage(UserId, message))