[nsajko]

I don't think testing against every existing dependent would make sense currently. The issue is the lack of tooling for mechanically checking whether the dependent accesses implementation details of the dependency, in which case it would be valid for the dependency to break the dependent.

There are some proposals to forbid the registration of a package release which trespasses on the internals of another package, though.

I hope someone tackles the above sooner or later, but another issue is the approach of testing every known dependent package might be very costly, both in terms of compute and manual labor, the latter because someone would have to do the work of maintaining a blacklist for packages with flaky unit tests. The good news is that this work might considerably overlap with the already existing PkgEval infrastructure. We'll see.