Added StepParent example

Author: jamie-allen

chapter04/src/test/scala/com/reactivedesignpatterns/chapter4/StepParentSpec.scala

@@ -0,0 +1,37 @@
+package com.reactivedesignpatterns.chapter4
+
+import org.scalatest._
+import akka.actor._
+import akka.actor.SupervisorStrategy.Restart
+import akka.testkit.TestProbe
+
+class StepParentSpec extends WordSpec with Matchers with BeforeAndAfterAll {
+  "An actor that throws an exception" must {
+    "Result in the supervisor returning a reference to that actor" in {
+      implicit val system = ActorSystem()
+      val testProbe = TestProbe()
+			val parent = system.actorOf(Props(new StepParent(testProbe.ref)), "stepParent")
+			parent.tell(Props[MyActor], testProbe.ref)
+			val child = testProbe.expectMsgType[ActorRef]
+      child ! TestMessage
+    }
+  }
+}
+
+case object TestMessage
+
+class StepParent(target: ActorRef) extends Actor {
+   override val supervisorStrategy = OneForOneStrategy() {
+     case thr: Throwable => target ! thr; Restart
+   }
+   def receive = {
+     case p: Props => 
+       sender ! context.actorOf(p, "child")
+   }
+}
+
+class MyActor extends Actor {
+  def receive = {
+    case _ => throw new NullPointerException
+  }
+}