When I was a rookie programmer 12 years ago, I was assigned a task to optimise a routine. It took current vehicle speed as input, performed integration and calculated total distance traveled. I made a mistake that was let through code review and was caught by an automated test. My calculations were off by 1% which accumulated to a larger amount in 10 minutes. After that incident we never had another bug for 5 years in that module. Does this make the tests invalid? Our does this improve confidence in our code?