Tests pattern statement using a pyang plugin and oc-ext:posix-pattern using goyang.
There is a demo CI workflow that runs on Pull Requests. They are used to demo the result of running the tests on the current YANG models. If they cause an expected test failure (perhaps because you added an uncaught corner case), it will not block merge and a minor version increment will be given.
Releases are synchronized with the current OpenConfig YANG models. If new breaking tests are added (e.g. test cases handled incorrectly by a current pattern regex), then the minor version must be incremented.
At this time, major version updates are not anticipated, but could occur as a result of major changes to the repository.