Code actions provider API for integration testing

Question

I'm writing a CodeActions provider in https://github.com/google/wireit/pull/174 and using an integration testing setup similar to that documented at https://code.visualstudio.com/api/working-with-extensions/testing-extension.

I can't seem to find any APIs to get the code actions that my language server provides, nor to get VSCode to apply a code action so that I may assert on the effects.