Comment by chasd00

What you're describing is basically perfect unit testing. There was even a trend called TDD ( test driven development ) that tried to make the tests the driving force behind building the software in the first place. It works but it has to be perfect and, inevitably, your tests need testing and so you're back to square one. Regardless, it's tedious and time consuming and shortcuts get taken then value of the whole thing falls apart and running the unit tests just becomes like a ritual with no real meaning/impact.