> ...but ultimately it's the tests that give you confidence. Pound the heck out of it in multithreaded contexts and test for consistency.

I don't think so.

Even on LLM generated code, it is still not enough and you cannot trust it. They can pass the tests and still cause a regression and the code will look seemingly correct, for example in this case study [0].

[0] https://sketch.dev/blog/our-first-outage-from-llm-written-co...