Create tests for the functionilty of mutationlevels on a more high level.

[Ja4pp]

Is your feature request related to a problem? Please describe.
We can do unit tests for every operator individually, but we should also test the new concept of mutation levels.

Describe the solution you'd like
Tests that verify the correct implementation of mutation levels on the stryker project.

Describe alternatives you've considered
N/A

Additional context
N/A