@mebymyself I am assuming you're finding it difficult to get access to the child to verify what messages it received. That's what I struggled with, at least. You could give the parent a Props as a constructor argument, that it would use to create its child. Replace the Props at testing time with one that produces a TestProbe. Or, your parent actor could have a virtual CreateChild() method; for testing the parent you can create a test double that inherits from the parent, and its overridden CreateChild() method returns a TestProbe or TestActor. One other approach that I have tried but didn't enjoy as much is for your child to log a Debug event upon receiving a certain message, and then use EventFilter expectation to prove that such a debug message is logged (presumably by the child) when you send a message to the parent.