Create a segment called "A/B one"
Add some contact lists
Scroll to the bottom where it says "select subset" and pick a randomized percentage or count
Create a segment called "A/B two"
Add some contact lists
Scroll to the bottom where it says "select subset" and pick a randomized percentage or count
Add a list membership rule in "A/B two" for "not in segment A/B one"
Add a list membership rule in "A/B one" for "not in segment A/B two"
You can send anything you want in a different broadcast to each segment, you're not limited to just testing subject lines or message bodies, you can test unlimited variables this way.