What do you suggest the alternative is? Also, I agree that's exactly what testing is, in fact I often now test code like that, get someone else to do one simpl

What do you suggest the alternative is? Also, I agree that's exactly what testing is, in fact I often now test code like that, get someone else to do one simple implementation in Python, a second high-performance implementation in C++/Rust, and compare them. Then, as long as the same bug doesn't occur in both versions (and that seems very unlikely, as they are implemented with different algorithms), we find all the bugs in both.