You can't get true 100% coverage* on digital hardware. (on quantum maybe!) so what to test or not is always a judgement call. Most of the time I'd assume the so

You can't get true 100% coverage* on digital hardware. (on quantum maybe!) so what to test or not is always a judgement call. Most of the time I'd assume the software stack is trustworthy but if you are doing something extreme you may want to test the compiler or even formally prove the compiler works as expected. * true as in all possible inputs and outputs rather than merely all code paths