test: Various fixes and improvements

[taratatach]

Various fixes and improvements of tests, especially scenarios, to help stabilize builds.

Please make sure the following boxes are checked:

• [x] PR is not too big
• [x] it improves UX & DX in some way
• [ ] it includes unit tests matching the implementation changes
• [ ] it includes scenarios matching a new behaviour or has been manually tested
• [ ] it includes relevant documentation