Well it’s not obvious that is true. If you ask LLM to write tests, it will generate versions of them that code passes, that doesn’t guarantee good code. If you write tests yourself and just pray for great LLM pull, it’s easier to just write code yourself, in my humble opinion
That's a useless approach as you point out but doesn't meant there isn't a valid testing regime to be explored and upheld. Manual testing is going to be a lot more important, I see QA teams/roles becoming very valuable assets in the coming years.