I also like the idea of extending the "standard" tests with your own "custom" tests if your app happens to rely on some undocumented behavior (Hyrum's Law). The

I also like the idea of extending the "standard" tests with your own "custom" tests if your app happens to rely on some undocumented behavior (Hyrum's Law). Then you get a nice error message when that observable behavior (not part of the contract) breaks, instead of the app falling over.