These would be similar to Documentation requirements, though may be slightly looser early on (as our Unit Test coverage is only currently limited to the core API). For example:
"All changes to core API must pass existing Unit Tests. Existing Unit Tests must also be updated when new methods are added to core API."
"New features are highly recommended to provide Unit Tests where plausible."
Meeting Notes
JIRA Catchup, 1.7 Updates & Schedule Reminder, Test Driven Development Policies