Once you have automated tests for your software, you must take care to keep those tests passing. With changes to the code or to infrastructure, or with new library versions, tests can start failing.
If you let them fail and don’t do anything against this creeping entropy, the diagnostic value of the tests starts to drop, and new regressions tend to be covered up by the general noise. Keeping your tests passing, and continuously checking in new features and bug fixes, is a practice that must be part of the engineering culture of a software development team. ...
