Review test namespaces

This issue is imported from pivotal - Originaly created at May 20, 2020 by Michiel Kodde

The test folder does not have an unambiguous namespace format. Some test namespaces include the Tests namespace, others dont. Adding the /Tests suffix messes with PSR autoloading (inspections). PHPUnit does not seem concerned with this at this point.

It might be a good idea to formalize the rules regarding test namespaces and syncronize all tests acording to those rules.

Other project projects have this tets namespace format:
Surfnet\ProjectName\Tests\Unit\Domain\ValueObject

With an underlying folder structure:
/project_root/tests/unit/Domain/ValueObject/SuperCoolTest.php

And a PSR-4 namespace definition:

    "autoload-dev": {
        "psr-4": {
            "ProjectName\\Tests\\": "tests/"
        }
    }

This personally works for me, feel free to suggest another style!

Start by reviewing the test folder, existing test namespaces, and the composer.json autoload-dev PSR-4 definition described in the issue. Compare namespace declarations with their folder paths and identify the convention to formalize. Done means the rule is documented or agreed and the affected tests are synchronized without disrupting PSR autoloading.