Sometimes, testing isn't only about what is in the ad, but also what isn't. Like testing an ad version that has a logo, and then doesn't. Or features a background, but then doesn't.
In this case, you need to create empty variant who doesn't display anything, versus the other versions which do.
Create an Empty Variant
Click Add Variant inside a variant group in the right panel
You can also remove an existing variant to create an empty variant. Click on the remove variant icon on the variant item