Setting up vitest for Immersive Web SDK

The projects created by the Immersive Web SDK use vite in a non-standard way, 

`iwsdk.config.json` is the project authority, not `vite.config.ts`.** It selectsthe active scene, the asset module, the component module, and all XR/worldfeatures. `vite.config.ts` only wires the plugin.

It’s not clear how to set up vitest, so I can add automated tests to my project.  I had Junie (the coding LLM from JetBrains tried a half-dozen ways to get vitest with Playwright and headless Chrome working, but they all failed with the error “Browser Mode was enabled, but provider was not specified anywhere.”

Is there a worked example of how to do this?