This is not correct on several levels. Reproducibility is not achievable in many real world scenarios, but worse it's not even very informative. Contra your a

This is not correct on several levels. Reproducibility is not achievable in many real world scenarios, but worse it's not even very informative. Contra your assertion, many people do some sort of regression testing like this but it's isn't terribly useful for verification or validation - but it is good at catching bad patches.