Ok. When I started with this exercise I couldn't write end-to-end tests because I couldn't express them - the data types where too complicated and I couldn't handle this. So I started with a sub-task and tests for this sub-task. But now The exercise is nearly finished (at least the original task), end-to-end test for this have been written, and most of the test cases in ConfigurationTest are indeed only duplicates of the end-to-end tests. I can send them to a peaceful retirement, they have fulfilled their purpose, they are obsolete now, and I don't need to maintain them in future.
Done.