> This has been solved already - automated testing.

This is specious reasoning. Automated tests are already the output of these specs, and specs cover way more than what you cover with code.

Framing tests as the feedback that drives design is also a baffling opinion. Without specialized prompts such as specs, you LLM agent of choice ends up either ignoring tests altogether or even changing them to fit their own baseless assumptions.

I mean, who hasn't stumbled upon the infamous "the rest of your tests go here" output in automated tests?