This is a good technique, and it's preferable to investing a bunch of effort into building a comprehensive suite of unit tests. But this technique is applicable

This is a good technique, and it's preferable to investing a bunch of effort into building a comprehensive suite of unit tests. But this technique is applicable to more than just core libraries; you can apply this to your entire stack, and to your services: Test that you don't break your reverse dependencies, by running those reverse dependencies, like in http://catern.com/usertests.html http://catern.com/usertests.html