[iron2disulfide]

I started my career off in the chip design world, where 100% line, branch, FSM transition, functional group, and toggle (i.e. individual bits in a bus switching 0 -> 1 _and_ 1 -> 0) was "table stakes". There are a lot of comments in here saying that achieving 100% coverage would be expensive - and they're right. The majority of headcount in modern chip design houses is taken up by verification engineers, whose sole job is to architect, implement and maintain a minimal test corpus that achieves that high bar. The cost of failure is simply too high to omit this step.

It was unsettling to me after moving to a SWE job where coverage was kind of... not as important.

[rTX5CMRXIfFG]

I can think of certain types of software that are so critical that they must be 100% thoroughly verified to be logically correct, e.g. software in surgical machines, airplanes, or high-frequency trading. The vast majority of applications, though, would survive with less coverage, though I still think that the sweet spot is somewhere between 70-80%.