What helps me with this inherent uncertainty is writing in a functional style (simple inputs and outputs, minimal functions) and using runtime tests to check fo

What helps me with this inherent uncertainty is writing in a functional style (simple inputs and outputs, minimal functions) and using runtime tests to check for correctness. The key is to have the tests as far down the abstraction tree as possible. There's a performance hit, but you can use macros to keep it out of production.