https://www.hyrumslaw.com/

your implementation is your interface. its a bit naive or hating-your-users to assume your tests are what your users care about. theyre dealing with everything, regardless of what youve tested or not.

Hyrum's law is about the real consumers/users (inadvertently) depending on any observable behaviour they can get their hands on.

TDD/BDD tests are meant to define the intended contract of a system.

These are not the same thing.