chore: use pytest for unit tests

[dariofaccin]

Description

This PR aims to remove unittest framework in favor of pytest, as described here.
Main changes:

• Use fixtures to configure patches

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have bumped the version of the library

[Gmerold]

Just some minor stuff.