Comment by xianshou

I believe the above comment refers to regression testing. For instance, if I write a test for an invariant that is fairly unlikely to change, then the chance that my behavior will change in the next hour based on the test run is small. However, if and when the invariant is mistakenly changed, even though negative side effects might not be immediately visible, it could be immensely valuable to me to see the flaw and restore that invariant.