[mdpye]

Right. Facepalm. I kind of missed the bit where we shifted paradigms.

My personal preference would still be to be explicit, to echew secret mutable state even in the tests, but that's just me. My personal baggage makes phrases like "then restore it after the test finishes" bring me out in a cold sweat ;)

I guess I sympathise with your colleague, but I agree it's not idiomatic, and not being idiomatic is not helpful in a team.