✅ Add unit tests

[ccamel]

Issue

In Pull Request #56, we implemented unit testing for the ontology using SHACL files to verify its compliance with quality standards and intended functionality. However, to maintain this high standard, it is crucial that we keep adding new tests. Consistently writing and executing tests will allow us to validate the ontology's structure and constraints, ensuring it is compliant and meets all necessary requirements throughout the development process. This approach will help us identify and rectify any issues with the ontology, ensuring it operates as expected when released and deployed.

Todo

• Identify areas of the ontology (including instances/examples) that are not yet covered by tests and that are of major interest for test writing.
• Write new tests to cover these areas.
• Ensure that the new tests are complete and meet established testing standards.