Router instance not found when testing component library integration

[amurf]

Reproduction

https://stackblitz.com/~/github.com/amurf/vue-router-component-library-integration

Steps to reproduce the bug

• Confirm navigation button works by clicking between three links in minimal reproduction dev server
• Close the dev server process
• Run pnpm test and it will fail with essentially router missing errors.

Expected behavior

As the Button component works as a router-link when running in dev mode or production builds, I would expect it to rendering correctly when running the test suite as well.

Actual behavior

The test will error with:

[Vue warn]: injection "Symbol(router)" not found.
[Vue warn]: injection "Symbol(route location)" not found.
[Vue warn]: Component is missing template or render function.
  at <RouterLink key=0 to="/about" replace=false >
  at <Button text="This will break in the tests" to="/about" >
  at <App ref="VTU_COMPONENT" >
  at <VTUROOT>

Additional information

We essentially want the Button component to support being a RouterLink when a to prop is passed, but we're finding it errors in the test suite.

I've done a bit a research of the other major UI libraries and noticed they are using similar-yet-different patterns to support this, so potentially we're just doing it wrong:

https://github.com/vuetifyjs/vuetify/blob/master/packages/vuetify/src/composables/router.tsx
https://github.com/epicmaxco/vuestic-ui/blob/develop/packages/ui/src/composables/useRouterLink.ts
https://github.com/quasarframework/quasar/blob/dev/ui/src/composables/private/use-router-link.js

But before going down this path wanted to raise it, as I feel like this shouldn't be so complicated and it was working for our tests before we wanted to use a real router for integration tests!

Any direction if I'm doing it wrong would be appreciated 🙏