First of all, thanks for this repo - it's full of wisdom and good ideas.
I was wondering if you had the chance to try vue-testing-library out. It is the port of dom-testing-library, which I believe is quite powerful and provides with a nicer starting point than using @vue/test-utils out of the box.
It favors rendering instead of shallow mounting, and provides with a "user-first" testing mindset - the additional queries focus on usability, and hidding methods such as "setState" help you avoind testing implementation details.
Again, thanks for this repo!