I am strong proponent of test-driven development and thus was quite envy of Sergei's test pack in libxklavier. I am glad to inform that the first test for keyboard layout switcher code landed in the repository and more to follow.
I am actually surprised how few tests we have in kdebase. It's not easy to test UI code (even though basic testing is not too hard with QtTest) but there's plenty of non-UI lines in kdebase that could benefit from some checking. Hopefully with David's improvements to KDE test framework we'll see more testing of the core functionality.