You can create an A/B split test of an actively running Facebook ad set by duplicating it. Here are the steps to getting this done…
New Feature: Facebook Creative Split Testing
Facebook creative split testing is an update of Facebook’s built-in split testing feature to help advertisers test to find the best-performing ad unit.
How to Use the Facebook Ad Split Testing Feature
Facebook has created a split testing feature that has simplified the process of uncovering the most effective targeting, optimization and placements.