Yes

Testing is not a formality. In fact, it's better and easier than ever. Tell your agents to develop your code-base with Red-Green-Refactor Test-driven development. Write failing tests first and run them, then write the code to make the tests pass, then refactor the code as needed. I used to hate writing tests before, but now that I can offload that (and the development, honestly) to AI, it's nothing to keep up with it. Your codebase quality will increase with TDD, because it will reduce the number of things that inadvertently break during updates. Things will break loudly and can be easily fixed (again, by AI) before shipping. If something does manage to get through, add more tests to cover it for next time.

This actually makes the LLMs better at coding as well. They can verify their own results and iterate with far less manual validation.