Currently, we have a working Bakery implementation, but we cannot be sure that our actors are doing what we expect them to do. Let's fix this by testing their behavior.

Testing actors is notoriously difficult because of their concurrent nature and message orientation. Luckily, in Akka Typed, an actor's behavior is just a function and thus can generally be tested in isolation. There are cases where we might want to test the interaction between actors, and in this case, it is inevitable to resort to asynchronous testing.

In synchronous setup, we create a behavior under test, send events that it should be able to react on, and verify that the behavior produces the expected effects (for example, spawning or stopping child actors) and sends further required messages.

The asynchronous scenario brings this approach into the context of a test actor system, which is close to a real one. We will see how this is done in practice in a moment.