I'd just pass in an IActorRef instead of doing this stuff with the TestKit in the constructor.

This test actor was a quick copy paste from the EchoActor in the Testkit. But your right. It could be done simpler

On the fence about this - it definitely adds deque semantics to the mailbox, but I'm now left wondering if we should be allowing stashing to work with the priority mailboxes in the first place.

If I think about it, the entire point of the prioritymailbox is to process messages in the order of the priority generator. FIFO no longer takes hold once you allow prioritization (across messages with different priorities - the StablePriorityMailbox should allow FIFO to occur within a priority.) So what good is stashing then? If I unstash a message I couldn't previously process, it either gets pushed back onto the queue in a totally different order (possibly not getting processed next) or if we stick with our normal double-ended queue semantics, it doesn't get processed in its normal priority order again.

I dunno, I'm leaning towards telling the users "don't use priority mailboxes with stashing." Either we just re-add messages we can't process back into the priority queue and re-prioritize them, which doesn't let us preserve message order (the re-added message will appear to be newer) or maybe we have to rewrite the prepend buffer to behave like a priority queue as well and process that first.

You are absolutely right. It does add some wierd semantics to the whole thing. I asked around on jvm akka channel about this. But haven't gotten any response as of yet.

The way this works now, is that messages are enqueued in the priority queue first. Then are handled by the actor, and then are stashed. Which means that messages are stashed in the order of priority as initially determined. When you unstash all, they are fed to the actor in that order as well.

This makes for some wierd behavior. Because it would seem to work when you simply stash all messages, and unstash all at a certain point. (see the spec i added as an example). But ofcourse this breaks down if you only intermittently stash and unstash a message.

Changing the prepend buffer to a priority queue wont solve this either. As that would mean the order would only be guarenteed within the context of the stashed messages, and not the mailbox in itself (the buffer of messages waiting will not be taken into account when determining priority)

Welp, I think my final thoughts on the subject are: let the users worry about their message orders. If they want to use stashing and priority mailboxes where the results aren't 100% predictable or stable, that's up to them.

Welp, I think my final thoughts on the subject are: let the users worry about their message orders. If they want to use stashing and priority mailboxes where the results aren't 100% predictable or stable, that's up to them.