testing actors

Hello,

What is the best way to test an actor. In particular, test how it handles messages that arrive in a particular order?

My use case: an actor sends a request message to another and waits for a response, another message may cancel the request and I'd like to test that the actor behaves correctly even if a response message is queued while handling the cancellation. So I'd like to queue both cancellation and response messages before letting the actor handle them

Regards,

Ittay