[dimgl]

I agree as well; I was confused as to how they benefited from switching away from Karma as a test runner. It seems that they simply replaced PhantomJS with jsdom, but in the process they lost Karma, which means that they can't run their test suite on other browsers.

Also, from first glance, I'm unable to see a performance improvement by not using Karma. It may be because they're using more tests in Mocha, but the difference isn't huge considering they're losing a lot of functionality.