This is true, but then the corrollary is that new PRs need to come with this higher, rigorous level of test coverage. And then that becomes a bit of a barrier

This is true, but then the corrollary is that new PRs need to come with this higher, rigorous level of test coverage. And then that becomes a bit of a barrier to contribution -- it's a tradeoff I often write an entirely new test harnesses for a feature, e.g. for https://www.oilshell.org https://www.oilshell.org, particularly using other implementations as "oracles". All of these run in the CI - https://www.oilshell.org/release/latest/quality.html https://www.oilshell.org/release/latest/quality.html The good thing is that it definitely helps me accept PRs faster. Current contributors are good at this kind of exhaustive testing, but many PRs aren't Even so, I do find myself simply adding test coverage from time-to-time -- that's an important job of a maintainer