> I imagine the tricky bit is testing the audio/video parts – "does the video work reliably with multiple participants" or whatever is probably quite hard to entirely judge in an automated fashion.

I actually forgot that Teams has audio and video. You are right about testing those two, I don't have a good idea for that either. I would probably look into using a virtual cam, like OBS implemented one, and then just check the footage on the other end?

But honestly, Firefox usually just works.