Full-Page Test (FPT) experiences are different. In an FPT experience, Monetate considers many factors before it decides whether to keep a customer on the base page or send them to a completely different URL. You can target those tests, and Monetate doesn't want you to lose that ability. This means that an FPT experience must be done in JavaScript once the browser has requested and seen the base content. In other words, an FPT experience can't be done using a server redirect (a 302 Temporary redirect).
Furthermore, Google appears to treat those as a permanent redirect (301).
FPT experiences, however, aren't a lost cause. You can give a hint to the search engines about what you're doing by ensuring the alternate page includes rel canonical information in the source code that points back to the original URL. This tells the search engines that you are not trying to hide different content under a page, but rather that the page that is specified is the canonical source and is the one that should be indexed.
Unfortunately, this is not something Monetate can do for you. Monetate works on the front end and modifies the page after it's served. This information sits in the <head> of the page and needs to be there when the page is served by your servers.
For experiences that redirect some customers to another page, it may also be very useful to add rel=nofollow to the HTML that you insert to tell search engines not to follow the link and index the next page. Where possible, you should avoid running Full-Page Test experiences for too long because this can also have an adverse effect on the way that Google measures page ranking.