Glad to finally see someone trying to popularize this kind of testing!
Multiple approaches for it were suggested in another thread last year.
The one I put there (oldnew_compat.yml · GitHub) gives nicer reports:
- doesn’t even try testing unresolvable combinations, no point in doing that
- indicates which specific dependency downgrade breaks the tests and how:
each GH job can be clicked on. - but is more expensive to run, does 2n tests – oldest/newest of each dep
So it can be applied to basically any package without fiddling with compats beforehand.