The only thing I dislike is what it chooses to test when asked to just "generate tests for X": it often chooses to build those "straitjacket for your code" style tests which aren't actually useful in terms of catching bugs, they just act as "any change now makes this red"

As a simple example, a "buildUrl" style function that put one particular host for prod and a different host for staging (for an "environment" argument) had that argument "tested" by exactly comparing the entire functions return string, encoding all the extra functionality into it (that was tested earlier anyway).

A better output would be to check startsWith(prodHost) or similar, which is what I changed it into, but I'm still trying to work out how to get coding agents to do that in the first or second attempt.

But that's also not surprising: people write those kinds of too-narrow not-useful tests all the time, the codebase I work on is littered with them!