>How do you tell that the calculations were done correctly? Presumably you have some way of doing that. Isn't that what we are discussing, how to tell if a pie

>How do you tell that the calculations were done correctly? Presumably you have some way of doing that. Isn't that what we are discussing, how to tell if a piece of code works? You could do a formal proof that the code works (which is long and tedious) or you can test it (less long and tedious but less rigorous). >You don't need tests if you only need to do it once. It doesn't matter how many times you plan on running it. What counts is how much we value the output. I wouldn't bet $20 that untested code works correctly.