It would be nice if we had the ability to run tests in a synchronous mode. That is, each call to mus runs a nested message loop until acked. This way we could easily tell if there is a problem, rather than possibly seeing a problem depending upon threading. Additionally I suspect for debugging a sync model would prove very helpful.

This should be possible with a stub implementation of a WindowTree that forwards the call to the real WindowTree and runs a nested message loop until the ack is received. I suspect this would entail some changes to WindowTreeClient to make sure it can deal with sync responses.