At what point should I trust projects like this?

I've heard stories of LLMs changing tests to get all the tests to pass instead of actually fixing code. So I'm not sure I trust it just because tests pass. I also think that tests do not and cannot check everything.

I also don't trust it just because it compiles in Rust. The Rust compiler does not check everything.

So at what point do projects like this cross from "untrusted" to "trusted"?