CheezTest lets you create and run Batcache-compatible server-side A/B tests in your theme. Learn more about how it works in the readme. There are also some examples you can follow.

The plugin makes use of Batcache’s support for vary_cache_on_function, which saves page variants in a page’s cache and then evaluates which one to serve when the page loads.

IMPORTANT: Since the tests run before Batcache, which in turn runs very early (before theme code is included), only built-in PHP functions and jetpack_is_mobile() can be used when defining tests. Any theme-specific functions will not be available.

The plugin was a joint collaboration between the team at I Can Has Cheezburger and VIP.