Increase the test coverage

[frostming]

Feature Description

This ticket will serve as a long-term plan, with the goal of improving the test coverage of the PDM project.

It is hoped that this will be a beginner-friendly contribution goal and thereby attract more contributors.

Problem and Solution

Check the overall coverage status at Codecov and feel free to choose a file to begin with.

Additional Context

No response

Are you willing to contribute to the development of this feature?

• Yes, I am willing to contribute to the development of this feature.

[deronnax]

suggest what uncovered parts could be the most beginner friendly. utils.py, maybe?

[Bonifacio2]

The coverage report mentioned in this issue's description's is not up to date. If it were, it would be easier to identify places that lack test coverage. What can we do about this?