Akka.net and Unit tests

I would like to use Akka.net TestKit for writing Unit tests, but I have a question. I have a class SubscriptionService which is responsible for transmitting messages to the selected actors.

public class SubscriptionService : ReceiveActor
{
    private readonly ActorSelection service1;

    private readonly ActorSelection service2;

    public SubscriptionService()
    {
        this.service1 = Context.ActorSelection("Service1");
        this.service2 = Context.ActorSelection("Service2");

        this.Receive<RequestMessage>(message => this.ProcessRequestMessage(message));
    }

    private void ProcessRequestMessage(RequestMessage message)
    {
        this.service1.Tell(message);
        this.service2.Tell(message);
    }

How can I test this behavior? I created this test but in this test I get the exception. "Additional information: Assert.Fail failed. Failed: Timeout 00:00:03 while waiting for a message"

[TestClass]
public class SubscriptionServiceUnitTests : TestKit
{
    [TestMethod]
    public void Test1()
    {
        var subscriptionServiceRef = this.ActorOfAsTestActorRef<SubscriptionService>("SubscriptionService");

        subscriptionServiceRef.Tell(new RequestMessage());

        var answer = this.ExpectMsg<RequestMessage>();
    }

I mean How can I get message for service1 and service2 in Test1 method ?