That means you can't use coverage tools, so this approach makes the tests unquantifiable. It is not how most major dev shops work, because of the bean counters and the "senior" developers/leads/managers/... who seem to want nothing but appeasing beancounters.
It also produces superior software in my experience.
Automatic test generation tools. There's quite a few on github, but the real ones are the ones you write yourself. What you're looking to do is to run the software a few times and record tests for particular pieces of code during those manual tests.
It also produces superior software in my experience.