如何在Akka集群中测试发行者到DistributedPubSub？

Question

我有一个演员，他的唯一职责是转发从外部接口(命令行、用户等)接收的消息。合适的话题。我想测试它是否正确地发布了这些消息。

我需要创建一些虚拟订阅者，他们将期望消息发布到某个主题，并对接收到的消息进行断言。

下面是我试图意识到的代码：

Messages.scala

case class Foo(foo: String)

InterfaceForwardingActor.scala

import akka.actor.{Actor, ActorLogging}
import akka.cluster.pubsub.{DistributedPubSub, DistributedPubSubMediator}
import com.typesafe.config.Config

/** Actor responsible for forwarding stimuli external to the system.
  * For instance, messages from the command-line interface or from a UI.
  *
  */
class InterfaceForwardingActor extends Actor with ActorLogging {
  import DistributedPubSubMediator.Publish

  protected val mediator = DistributedPubSub(context.system).mediator

  log.info(s"Hello from interface forwarder.")

  final val topic = "info"

  def receive = {
    case foo: Foo => {
      log.info("Forwarding a Foo message")
      mediator ! Publish(topic, foo)
    }
  }  
}

以及测试代码

InterfaceForwardingActorTest.scala

import akka.actor.{ActorSystem, Props}
import akka.cluster.client.ClusterClient.Publish
import akka.cluster.pubsub.DistributedPubSub
import akka.testkit.{ImplicitSender, TestKit, TestProbe}
import com.typesafe.config.ConfigFactory
import org.scalatest.{BeforeAndAfterAll, Matchers, WordSpecLike}

class InterfaceForwardingActorTest extends 
    TestKit(ActorSystem("InterfaceForwardingActorSpec")) with ImplicitSender with 
    WordSpecLike with Matchers with BeforeAndAfterAll {

  override def afterAll {
    TestKit.shutdownActorSystem(system)
  }

  "An InterfaceForwardingActor" must {
    val interfaceForwardingActor = system.actorOf(Props[InterfaceForwardingActor])

    val probe = TestProbe()
    val mediator = DistributedPubSub(system).mediator

    // subscribe the test probe to the "info" topic
    mediator ! Publish("info", probe.ref)

    "publish a Foo message" in {
      val msg = Foo("test")
      interfaceForwardingActor ! msg
      probe.expectMsg(msg)
    }
  }
}

我发现，订阅了probe主题的info不会在3秒的默认超时时间内接收消息，断言失败。然而，有趣的是，我确实看到了日志消息，说明接口转发参与者确实在转发Foo消息。

我在考试中做错了什么？

Answer 1

TestProbe应该订阅测试代码中的主题：

mediator ! Subscribe("info", probe.ref)

而不是

mediator ! Publish("info", probe.ref)

分布式发布-订阅的文档页是这里，以供参考。