LLMs are very good at looking at a change set and finding untested paths. As a standard part of my workflow, I always pass the LLM's work through a "reviewer", which is a fresh LLM session with instructions to review the uncommitted changes. I include instructions for reviewing test coverage.

I've also found that LLMs typically just partially implement a given task/story/spec/whatever. The reviewer stage will also notice a mismatch between the spec and the implementation.

I have an orchestrator bounce the flow back and forth between developing and reviewing until the review comes back clean, and only then do I bother to review its work. It saves so much time and frustration.