Akka中的Reaper模式将其Terminated消息发送到死信箱

Question

我一直在尝试Akka团队建议的reaper pattern。它在理论上听起来不错，但提供的单元测试不会传入sbt或Eclipse的JUnit运行程序。

import scala.concurrent.duration._
import akka.util.Timeout
import akka.actor._
import akka.testkit.{TestKit, ImplicitSender, TestProbe}
import org.scalatest.{WordSpec, BeforeAndAfterAll}
import org.scalatest.matchers.MustMatchers
import org.scalatest.junit.JUnitRunner
import org.junit.runner.RunWith

@RunWith(classOf[JUnitRunner])
class ReaperSpec extends TestKit(ActorSystem("ReaperSpec"))
    with ImplicitSender with WordSpec with BeforeAndAfterAll with MustMatchers
{
    import Reaper._

    override def afterAll() {
        system.shutdown()
    }

    // Our test reaper. Sends the snooper a message when all the souls have been reaped
    private class TestReaper(snooper: ActorRef) extends Reaper {
        def allSoulsReaped(): Unit = snooper ! "Dead"
    }

    "Reaper" should {
        "work" in {
            // Set up some dummy Actors
            val a = TestProbe()
            val b = TestProbe()
            val c = TestProbe()
            val d = TestProbe()
            // Build our reaper
            val reaper = system.actorOf(Props(new TestReaper(testActor)))
            // Watch a couple 
            reaper ! WatchMe(a.ref)
            reaper ! WatchMe(d.ref)
            // Stop them
            system.stop(a.ref)
            system.stop(d.ref)
            // Make sure we've been called
            within (1 seconds, 5 seconds) {
                expectMsg("Dead")
            }
        }
    }
}

在向演员添加日志后，我注意到Terminated消息最终出现在死信框中。所以收割者演员从来没有得到终结的信息。

[ERROR] [08/05/2014 11:10:27.244] [ReaperSpec-akka.actor.default-dispatcher-4]
    [akka://ReaperSpec/user/$a] Monitored actor [Actor[akka://ReaperSpec/system/testActor2#-1060476766]] terminated (akka.actor.DeathPactException)
[INFO] [08/05/2014 11:10:27.248] [ReaperSpec-akka.actor.default-dispatcher-2]
    [akka://ReaperSpec/user/$a] Message [akka.actor.Terminated] from Actor[akka://ReaperSpec/system/testActor5#2029818496] to Actor[akka://ReaperSpec/user/$a#1787786349] was not delivered.
    [1] dead letters encountered, no more dead letters will be logged. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.

我认为system.stop(watchedActorRef)可以保证向正在观看watchedActorRef的所有演员发送终止消息。我错过了什么？