Enhance `RunResult` warning assertion capabilities

while writing some other bits and pieces, I had a use case for checking the warnings omitted, RunResult has a assert_outcomes() that doesn’t quite offer warnings= yet the information is already available in there, I suspect there is a good reason why we don’t have assert_outcomes(warnings=...) so I propose some additional capabilities on RunResult to handle warnings in isolation.

With assert_outcomes() the full dict comparison may get a bit intrusive as far as warning capture is concerned.

something simple like:

result = pytester.runpytest(...)
result.assert_warnings(count=1)

Thoughts?

[symonk]

@nicoddemus sweet, will implement it this weekend, I wanna get a look at per-logger configuration/suppression as a capability as well

[nicoddemus]

Yeah I think that’s a natural addition. 👍 I didn’t take a closer look at #8952 because it was closed by the time I got to it, hehehe.