Set up mocha testing infrastructure on all UV repositories

[hackartisan]

Component-level unit tests; UV-level integration tests. to support testing current behavior a la pub/sub architecture.

[LlGC-szw]

All issues will be triaged for further investigation or closure by the 28 September 2023. If your issue is still relevant and would like for it be investigated further please comment by 14 September 2023.

[demiankatz]

Seems worth discussing this (and other test-related tickets like #569 and #572) in a future steering group meeting. Not sure that we necessarily want to lock in on Mocha at this point, but we should come up with an overall test strategy.