alt Hacker NewsYes, regression tests are not enough. One generally has to think through code repeatedly, with different aspects in mind, to convince oneself that it is correct under all circumstances. Tests only point-check, they don’t ensure correct behavior under all conceivable scenarios.
Unless you are in the business of writing flight control software, OS kernels, or critical financial software, I don't think your own code will reach the standards you mention. The only way we get "correct under all conceivable scenarios" software is to have a large team with long time horizons and large funding working on a small piece of software. It is beyond an individual to reach that standard for anything beyond code at the function level.