There is a critical distinction between tests and formal specification/verification. It is not sufficient to make a bunch of tests if you want to ensure behavior. Formal methods have long been recognized. If a programmer is only now realizing their necessity due to LLM code synthesis, I do not trust the programmer with human-generated code, let alone LLM-generated code. I don't expect everyone to formally verify all code for many reasons, but the principles should always be present for any program more serious than a hobby project. Take a look at [0]. Cautious design is needed at all levels; if tests or formal methods are relied upon, they count.

[0] https://news.ycombinator.com/item?id=43818169