If one of your key metrics is rate of returns, surely this would show up in an A/B test. You could also check for it in usability testing by making the task som

If one of your key metrics is rate of returns, surely this would show up in an A/B test. You could also check for it in usability testing by making the task something where the user would be interested in the "fine print details" if they were visible enough for the user to notice.