[Fix] Fixed failing unit tests

[viniarck]

Fixes #27 that @italovalcy has reported

Description of the change

• We've had some failing assert calls on listen_to decorators being these were being tested out directly, and depending on the threadpool queue/scheduler there's no guarantee it'll be immediately or shortly after executed, since we don't expose a join/result, the safest route to be deterministic was to extract the listen_to handlers in new methods, and test hem out without depending on threading spawn execution times.

[viniarck]

thanks for reviewing, @italovalcy