Hi,
So if I understand correctly you AB tested with two pages (for example: domain.com/page and domain.com/testpage) and both were indexed by Google? If yes, than option 2 as you mentioned is the best way to go here.
For the future I would recommend to make sure that the testpage is not indexed by Google via robots.txt/meta noindex or use the rel canonical tag. You don’t want the testpage to get organic traffic here to prevent issues.