Akka: [akka 2.5.2 TestKit] testActor receive duplicate message.

Created on 27 May 2017 · 3Comments · Source: akka/akka

In the following code, I just send one message (int 1) to the testActor,
but in expectMsgPF, it receive duplicate messages (two 1s).
Please help.

import akka.actor.AbstractActor;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.testkit.javadsl.TestKit;

public class Main {
    public static void main(String[] args) {
        ActorSystem system = ActorSystem.create("system");

        new TestKit(system) {{
            ActorRef sender = system.actorOf(SendingActor.props(getTestActor()), "sender");
            // just send 1 once.
            sender.tell(1, getRef());

            expectMsgPF("test", m -> {
                // print 1 twice.
                System.out.println(m);
                return 0;
            });
        }};

        TestKit.shutdownActorSystem(system);
    }
}

class SendingActor extends AbstractActor {
    private ActorRef receiver;

    static Props props(ActorRef receiver) {
        return Props.create(SendingActor.class, receiver);
    }

    public SendingActor(ActorRef receiver) {
        this.receiver = receiver;
    }

    @Override
    public Receive createReceive() {
        return receiveBuilder()
                .matchAny(o -> {
                    receiver.tell(o, self());
                })
                .build();
    }
}

help wanted core

Source