Re-enable tests

[gossi]

As part of #689 I deactivated a couple of tests, since the test-setup with fixtures had cyclic dependencies.

This needs to be reworked as part of this ticket and make tests available again through vitest.

Somewhen during development - I thought - it was possible to run vitest wo/ having the code build before. As part of this ticket, investigate, if bringing back vite to each ticket (with its config), it can run tests wo/ them being built by tsup.