Wednesday, July 13, 2016

Testing your Akka.NET actors using TestKit

Due to the nature of Actor based systems, they can be complex to test. Luckily Akka.NET, the actor framework of my choice, is accompanied by Akka.TestKit, a library that makes it easy to unit test Akka.NET actors.

How to get started?

Akka.TestKit has support for the most popular test frameworks for .NET; MSTest, XUnit and NUnit.

As I’m a long time NUnit user, I show you how to set it up using NUnit, but the steps for other frameworks are similar.

Step 1- Download the correct NuGet Package

For every test framework a seperate NuGet package is available, as I will use NUnit, I download the Akka.TestKit.NUnit3 nuget package. (If you are still using an older NUnit version, a separate package is available; Akka.TestKit.NUnit.

Step 2 – Initialize your test class

Every test class should inherit from TestKit. This class provides all the necessary wiring, setup and cleanup of the actor system and a range of helper methods.

Step 3 – Create an actor

Inside every test an ActorSystem instance is created making each test completely isolated. This ActorSystem is available through the Sys property on the TestKit class. You can create an actor using the Sys property or use the ActorOfAsTestActorRef method:

Step 4 – Send messages to your actor

Once your actor system is created, it’s time to start sending some messages:

Step 5 - Assert for results

Finally you can check for results. If you don’t expect any messages to be returned, you can use ExpectNoMsg() otherwise you can use the ExpectMsg() method:

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