Eliminate sleep calls from tests #2
Description
The unit tests currently use a few calls to sleep with very small waits in order to give control to the thread.
These calls don't hurt "much" to the test time because the few tests we have run in a couple seconds anyway. However, it probably is a smell of a lack of understanding of how we interface with the gem.
For example, if the gem was a regular Thread, the proper way of handling control to it would be to wait. However, the gem it's not really a thread, so this is not possible.
The point of this task is to go in that direction: think (and implement) a way to test UniqueThread in a similar way that one would deal with a regular Thread