I use CodeCompanion on neovim. My workflow for text fixtures is basically:

""" Given these files: file1, file2, ... (these are pulled entirely into the LLM context)

Create a test fixture by creating a type that implements the trait A and should use an in memory SQLite DB, another one that implements Trait B, ...

"""

Of course there is a bit of back and forth, but I find that using Interfaces/Traits/ABCs extensively makes LLMs perform better at these tasks (but I believe it is a nice side-effect of having more testable code to begin with).

However, wiring with IoC frameworks are a bit of a hit and miss to be honest so often I still have to do these parts manually.