unit tests for lazy loading strings

[IngmarEckhardt]

Description:
The integration of unit tests for the String Repository is currently pending due to dependencies on issue #8. Once the refactoring outlined in issue #8 is completed, it is crucial to implement unit tests for the String Repository. The goal is to achieve a minimum of 90% code coverage, considering both covered lines and branches.

User Story:
As a developer, I anticipate a 90% code coverage in open-source, visible tests to instill trust in the utilized library.