As for the xlib stuff, I can't really write tests for that. But I will write a more extensive test suite for the core components, especially the ones in src/core.rs

For the methods in window_manager.rs, they often depend on the window system, but that shouldn't be a problem as I could simply insert a dummy interface.

Tests will follow. Last weeks were just filled with thesis and preparations for my last exam. So I used the coding for relaxation and kinda omitted the tests. I know, I know...behaviour.