Karma, Angular.JS "Module is not available!" error

I was troubleshooting "Module '{0}' is not available!" error while testing an Angular.js app with karma and it got me puzzled quite a bit. Worst of all -- Google was not helpful (which clearly indicated that the problem is at my end). This url: http://docs.angularjs.org/error/$injector:nomod did not help either. My problem was that I forgot to include my controller js file into the files: [] array in karma configuration. Doh!