you start Ping and then, he plays with Pong (which is a better player that can smash).Ping can "survive" one smash and then he "becomes" vulnerable => next smash he looses.

PingPongActor.scala

case object Ball
case object SmashedBall
case object PleaseServe
case object YouWin

class Ping(pong: ActorRef) extends Actor {

    override def receive = {
        case PleaseServe =>
        println("Serving")
        pong ! Ball
        context.become(fresh)
    }

    def fresh : Receive = {
        case Ball =>
        returnBall()
        case SmashedBall =>
        returnBall("Ha! Caught one!")
        context.become(vulnerable)
    }

    def vulnerable : Receive = {
        case Ball =>
        returnBall()
        case SmashedBall =>
        println("Not again! ... You win Pong!")
        pong ! YouWin
        context.stop(self)
    }

    def returnBall(message : String = "ping") = {
        println(message)
        pong ! Ball
    }
}

class Pong extends Actor {
  val reload = 5

  override def receive = preparingForSmash(reload)


  def preparingForSmash(leftBeforeSmash : Int) : Receive = {
    case Ball if leftBeforeSmash == 0 =>
    println("Try catch this one!")
    sender ! SmashedBall
    context.become(preparingForSmash(reload))
    
    case Ball =>
    println("pong")
    sender ! Ball
    context.become(preparingForSmash(leftBeforeSmash - 1))
    case YouWin =>
    println("I'm so good!")
    context.stop(self)
    context.system.shutdown()
}
}

object TennisMatchTest extends App {
  val system = ActorSystem("TennisMatch")
  val pong = system.actorOf(Props[Pong], name = "PlayerTwo")
  val ping = system.actorOf(Props(new Ping(pong)), name = "PlayerOne")

  ping ! PleaseServe

  system.awaitTermination
  println("match is over let's go home!")
}