Testing ad copy works the same way testing a landing page does: change one meaningful variable at a time and let the data reach significance before acting.
Test One Element at a Time
Changing the headline, description, and call to action simultaneously makes it impossible to know which change actually drove the result.
Give Tests Enough Volume
Calling a winner after a handful of clicks on a low-traffic campaign is a recipe for chasing noise instead of signal.
Document What You Learn
Even an inconclusive or losing test teaches you something about what resonates with your audience, so keep a record you can build on.
Next step: Use the Word Counter to make sure your ad variants fit within character limits before you launch a test.