How to create actor with parameterized constructor from testprobe

Question

I am trying test to MyActor for sending a MessageB to itself on condition. MyActor takes setting as constructor parameter. Setting doesn't have setter cause it is intended to be immutable after creation.

public class MyActor : ReceiveActor
{
    private bool Setting { get; }

    public MyActor(bool setting)
    {
        Setting = setting;

        Receive<MessageA>(message => HandleMessageA(message));
    }

    public void HandleMessageA(MessageA message)
    {
        if (Setting)
            Self.Tell(new MessageB);
    }
}

And here is the test

[Test]
public void HandleMessageA_SettingIsTrue_MessageBIsSent()
{
    bool setting = true;
    var testProbe = this.CreateTestProbe();
    var myActor = Props.Create<MyActor>(testProbbe);

    myActor.Tell(new MessageA);

    myActor.ExpectMsg<MessageB>();
}

My problem is that i don't know how to pass bool setting to constructor. Well I can write it like this

bool setting = true;
var myActor = Props.Create<MyActor>(setting);

And this way myActor will have settings set. But than I didn't use TestProbe and therefore will not be able to listen for expected message. So my question is how make Arrange section of test correctly?

score 1 · Answer 1 · answered Oct 12 '18 at 15:57

A great guide to testing with Akka.NET describes how to create actors within the test system:

Create your actors within Sys so that your actors exist in the same ActorSystem as the TestActor.

// create an actor in the TestActorSystem
var actor = Sys.ActorOf(Props.Create(() => new MyActorClass()));

score 0 · Answer 2 · answered Oct 15 '18 at 13:58

Well the situation you have created is rather artificial. Because in a real world scenario you would either send MessageB to another actor. Which you would then be able to substitute with a TestProbe. Or you would verify the sideeffect that your messageB would have. So for example sending messageB to Self, would update some property on your actor, which you could then Test for.

Also see Chima's response, he shows the correct way to create your actor. Because only instantiating the Props is not enough.

And some general advice. When testing actors, you will want to try to refrain from testing for individual messages. Try and test the outcome (or side-effect) of sending those messages instead. That way your tests are a lot less brittle should you ever refactor your Actor's interactions

How to create actor with parameterized constructor from testprobe

2 Answers2