[randomdata]

This is why I'm not sure more languages don't instil the idea of "public" and "private" tests like Go does.

Your "public" tests should document the API for future programmers. This is the concrete contract that should never change, no matter what happens to the implementation. If these tests break, you've done something wrong.

Your "private" tests are experiments that future programmers know can be removed if they no longer fit the direction of the application.

[kubanczyk]

So, test the compatibility guarantee (of your major number in semver).

How is this formalized in Go?