scala - TestActorRef : Could not get the underlyingActor, 什么也没说

Question

我正在尝试为以下 Actor 编写我的第一个 ScalaTest

object Runner {
  def props(race: Race) = Props(classOf[Runner], race)
}

class Runner(race: Race) extends Actor with ActorLogging {

  import context.dispatcher

  @throws[Exception](classOf[Exception])
  override def postRestart(reason: Throwable): Unit = context.parent ! RestartRunner

  override def receive: Receive = LoggingReceive {
    case Start => {
      log.debug("running...")
      for (i <- 1 to 3) {
        Thread.sleep(200)
      }
      throw new RuntimeException("MarathonRunner is tired")
    }

    case StartWithFuture =>
      log.debug("I am starting to run")
      race.start pipeTo self

    case Failure(throwable) => throw throwable

    case Stop =>
      log.debug("stopping runner")
      context.stop(self)
  }
}

所以，我愿意

import akka.actor.{Props, ActorSystem}
import akka.testkit.{TestActorRef, TestKit}
import org.scalatest._

class RunnerSpec extends TestKit(ActorSystem("test"))
with WordSpecLike
with MustMatchers {
  "A Runner Actor" must {
    val runner = TestActorRef(Props(new Runner(new Marathon)))
    "receive messages" in {
      runner ! Start
      runner.under <== says Nothing (see attachment)
    }
  }
}

但我看到的是

为什么我不找回 Runner Actor？

Answer 1

由于 Props 是未类型化的，它不知道将构建哪种类型的 actor(在您的例子中是 Runner)。因此，TestActorRef 也无法推断类型。这就是为什么在使用

构建 TestActorRef 时需要显式声明底层 actor 的类型的原因

val runner = TestActorRef[Runner](Props(new Runner(new Marathon)))

如果您的 Actor 不需要任何参数，这甚至可以缩短为

val runner = TestActorRef[Runner]

但是，由于 Nothing 实际上是每个 Scala 类型的基类，所以在这两种情况下，底层参与者都是相同的。因此，如果无法更改 TestActorRef 定义，也可以强制转换为生成 Runner。

runner.underlyingActor.asInstanceOf[Runner]