Do you let LLMs write both your tests and your code?

I'm curious what stance others have taken? Or what they've experienced with this? I'm toying with adding a rule to our values.md that the LLM can only significantly generate one or the other. I'm reviewing a merge request at the moment where it's clear the LLM mostly did both, and they're highly tautological. And I can see how it over engineered the code, just to be able to write more tests almost.