Publishers can launch A/B tests of account-level settings to allow or block:
General ad categories (including first level sub-categories)
Sensitive ad categories
Ad serving opt-outs (e.g., enhanced text ads, expandable ads, etc.)
Running A/B tests doesn’t require any additional or alterations to the AdSense tracking code. However, just one global account-level test or ad settings test can run at one time.
You’ll find more on setting up and evaluating test performance here.
via Marketing Land