FWIW, writing implementation is much more pleasant/interesting experience, because you're writing the actual thing the application is supposed to do. In contrast, when writing tests, you're describing what the application is supposed to do, using an extremely bloated, constrained language, requiring you to write dozens or hundreds of lines of setup code, just to be able to then add few glorified if/else statements.

In my experience, at least in languages like C++ or Java, unit tests are made of tedium, so I'm absolutely not surprised that the first instinct is to use LLMs to write that for you.