It's true that tests are very helpful for this. However there are a lot of bugs in the wild that are difficult to reproduce, especially ones that will only crop

It's true that tests are very helpful for this. However there are a lot of bugs in the wild that are difficult to reproduce, especially ones that will only crop up under rare conditions of state. It's as Linus said- "There really are only two acceptable models of development: think and analyze or years and years of testing on thousands of machines". Years and years of testing on thousands of machines happens to be the best predictor of code that runs correctly.