There are thousands of projects out there that use mocks for various reasons, some good, some bad, some ugly. But it doesn't matter: most engineers on those projects do not have the option to go another direction, they have to push forward.

In this context, why not refactor (and have your LLM of choice) write and optimize the integration tests for you? If the crux of the argument for LLMs is that it is capable of producing sufficient quality software and dramatically reduced costs, why not have it rewrite tests?