I'm experiencing the same confusion, there doesn't seem to be an associated button in the Vue SFC Playground that can run a test, nor is there a command line.But I do found out a solution for lazy person (like me).

The author of this repo has put the project documentation on a website, where the Chinese version gives a new link for each challenge, jumping to the "stackblitz" website to run the tests automatically, the link to this documentation is: "https://cn-vuejs-challenges.netlify.app/questions/1-hello-word/readme.zh-cn.html"

so you can modify App.vue in this website for auto test.

Hope will help