How to write automated tests for zsh completion?

I have a project in which I automatically generate zsh completion functions. As I work on it, I've found corner cases and bugs which I'm just writing down and making sure to re-test when I make changes. Obviously, I want to write a proper testsuite, but I can't figure out how. For bash completions, testing is quite easy -- set COMP_* variables, run the function, and check COMP_REPLY. I'd like to do something similar for zsh. I've read the compsys docs to the best of my ability, but I'm not seeing a solution. I'd like to set the context by hand, run my completions, and then see an array of descriptions or something. Has anyone found a way to test completions?