DOC: Update Testing Actor Systems (TestKit) Chapter. See #1486

akka-docs/scala/code/akka/docs/testkit/PlainWordSpec.scala

@@ -0,0 +1,44 @@
+package akka.docs.testkit
+
+//#plain-spec
+import akka.actor.ActorSystem
+import akka.actor.Actor
+import akka.actor.Props
+import akka.testkit.TestKit
+import org.scalatest.WordSpec
+import org.scalatest.matchers.MustMatchers
+import org.scalatest.BeforeAndAfterAll
+import akka.testkit.ImplicitSender
+
+object MySpec {
+  class EchoActor extends Actor {
+    def receive = {
+      case x ⇒ sender ! x
+    }
+  }
+}
+
+//#implicit-sender
+class MySpec(_system: ActorSystem) extends TestKit(_system) with ImplicitSender
+  with WordSpec with MustMatchers with BeforeAndAfterAll {
+  //#implicit-sender
+
+  def this() = this(ActorSystem("MySpec"))
+
+  import MySpec._
+
+  override def afterAll {
+    system.shutdown()
+  }
+
+  "An Echo actor" must {
+
+    "send back messages unchanged" in {
+      val echo = system.actorOf(Props[EchoActor])
+      echo ! "hello world"
+      expectMsg("hello world")
+    }
+
+  }
+}
+//#plain-spec