A JUnit 5 Extension for testing Akka and Akka Streams

For an existing project we are using Akka with JUnit 5.

Akka is an amazing toolkit which has an implementation of the actor model (akka-actors) as well as the reactive streams (akka-streams) and already comes with a handy test kit as well. However for using the test kit you will still need to setup Akka components like ActorSystem or ActorMaterializer yourself. In order to make this a bit more convenient using JUnit I decided to create a small extension takes care of the lifecycle of those two components during test.

JUnit 5 extensions allow you to setup your testing harness. It provides certain hooks which are called before, during and after the tests, your extension can use a context object in which it can store its state. An extension can resolve test method parameters effectively injecting the components it is managing into each test method.

The little AkkaJunitExtension I have created can easily be used. The following test is a short demonstration of that:

@ExtendWith(AkkaJunitExtension.class)
@AkkaJunitExtensionConfig(name = "test")
class SomeAkkaJunit5Test {

    @Test
    void system_is_present(ActorSystem system){
        assertThat(system).isNotNull();
    }

    @Test
    void system_has_name(ActorSystem system){
        assertThat(system.name()).isEqualTo("test");
    }

    @Test
    void actormaterializer_is_present(ActorMaterializer mat) {
        assertThat(mat).isNotNull();
    }
}