PR Dashboard: add better tests based on real PRs

[trask]

Even to just encode current behavior on current PRs. Including ones that have been reported as problematic, e.g. #106

[harshilv17]

hey @trask, may I would like to write up the tests, may you please assign it to me.

[trask]

hi @harshilv17, thanks for your interest in the project! I think I'd like to implement this because I have some ideas in mind about how to implement it but need to work through those ideas a bit more first

[harshilv17]

Alright @trask sir, no issues. Please go ahead with it...