[ensiferum]

That doesn't sound right. Unit testing happens very close to the unit you want to test, i.e. class or function most of the time. Most of these should be designed with testing in mind so they're actually something you can write unit tests for. And there ought to be a whole bunch of classes/functions/components that can be tested this way, such as scripting code, networking code audio code etc.

It's not hard and definitely not impossible. Just requires a mind set towards quality and testing.