This is the key to the whole thing in my opinion.
If you ask a coding agent to port code from one language to the another and don't have a robust mechanism to test that the results are equivalent you're inevitably going to waste a lot of time and money on junk code that doesn't work.
Fuzzing handles the logic verification, but I'd be more worried about the architectural debt of mapping GC patterns to Rust. You often end up with a mess of Arc/Mutex wrappers and cloning just to satisfy the borrow checker, which defeats the purpose of the port.