Yup I've used Vitest without Vite for a personal project. I replaced Jest as I was having a lot of trouble with ESM modules (it might be better now)

Thanks! I'll definitely take a closer look - "better than Jest" is a great place to start, but not if it means boiling an ocean first.

I'm pretty sure you can. Though I haven't tried it myself I did a search if we could integrate it into our Next.js app (Next uses Webpack internally) and found this: https://github.com/elpnt/nextjs-vitest-example