For better or worse I've been working on the same codebase for almost a decade; now whenever I patch the code I've got half an eye on how likely it is that I or

For better or worse I've been working on the same codebase for almost a decade; now whenever I patch the code I've got half an eye on how likely it is that I or someone else could accidentally break this code in the future. If you've got to write code that's not allowed to fail, you can't afford set up little traps like this for yourself.