How do you handle testing and test-suite pollution when using automated coding agents?

Whenever I let an agent implement a new feature, it either writes brittle tests that pass by mocking everything out of existence, or it outright deletes existing integration tests that fail because of its changes.

For teams relying on AI for feature development and test coverage how do you ensure the test suite remains genuinely robust and trustworthy?

What workflows do you use to review and validate the tests generated by your coding assistants?