I would request in the PR references to the unit test with 100% coverage. Once I run it and if it passes I would do a spot check and look for glaring errors. Nothing deep. Perhaps I would run lint or some static analysis tool on the code. If the analysis tools come out squeaky clean and the unit test passes? Well, what's not to like? One or more problems? Reject the whole thing.
The problem is you can get a very large, messy, and inconsistent code base that eventually will slow things down. Even if tests pass, the code can be a detriment in the long run.
The PR will be huge, plus AI is great at adding tons of shallow tests.
I see tests as little pins that hold your codebase down. They can be great for overall stability, but too many and your project becomes inflexible and brittle.
In this case you’d be nailing a bunch of code that you don’t want to the code base.
