Impact of A/B testing on Search Engine Optimization (SEO)
Matt Cutts: Split Testing Is Approved By Google
Will using Visual Website Optimizer negatively affect your SEO rankings?
Here is a link to an article with more information about the topic.
UPDATE: There’s official confirmation from Google’s Matt Cutts that split testing does not impact search rankings
So, to answer your question, no. you don't need to worry about your A/B testing having any effect on your SEO.
(I should add - if you've written your own server-side A/B testing platform - that could theoretically have some effect on your SEO, but it would be negligible if any. And it could be fixed by not running A/B tests for Google bot.)