Google Has recently introduced easy A/B experiments in AdSense dashboard. Previously A/B testing was a bit of hassle for publishers, but from now they will be able to easily configure A/B Experiments from their adsense dashboard. Here is the official Announcement: http://adsense.blogspot.in/2013/11/ab-experiments-for-ad-unit-settings.html
Unfortunately, those of us who use DFP to deliver AdSense and other types of advertising aren't able to take advantage of it. I'm looking forward to the day when DFP is upgraded.