> I start to see a lot of these re-writes that depend on tests to state that its working.

There's another way to validate the rewrite though. Just run both pgrust and postgres and compare the output. Know of an edge case? Run it too. Doesn't know? Use a fuzzer or some automated tool to find interesting inputs. Found an inconsistency? The input/output pair becomes a test case now

Not sure if there's tooling for that though. If there is, just give it to Claude so they will incorporate it in their development loop