phpunit: 7 errors, 7 total tests

Problem/Motivation

Running the new test gitlab-ci tests phpunit is allowed to pass, but it should be fixed:
https://git.drupalcode.org/project/dopl/-/jobs/3312147

Steps to reproduce

Run phpunit

Proposed resolution

Review the phpunit test results to evaluate the issues and fix them.

Remaining tasks

Fix the code to allow the tests to pass.
Commit the code
Re-run phpunit