So I think you are running on a false premise here efarrer. The false premises is that anyone ships bug free code. It can be done but it's stupidly expensive.

So I think you are running on a false premise here efarrer. The false premises is that anyone ships bug free code. It can be done but it's stupidly expensive. Formal methods Z proofs, etc. Unit testing and static typing are 2 different techniques which eliminate bugs. The question that needs to be answered is which of the 2 techniques is the most effective per developer hour spent. Unit tests do not caught all the bugs that static typing would catch nor does static typing catch all the bugs unit tests would catch. That's not an useful observation. Nor is there a moral here that you should be doing both, doing both is expensive and costs $$$.