Your visitor is very close to buying from you but still didn’t. Maybe he just abandoned his shopping cart without paying, or he read many different articles and sales letters about your product and still didn’t buy.
If you have an arsenal of testimonials, put the visitor on an automated sequence (email, Facebook ads, etc.) and only use one testimonial for each communication in the series. Just bombard them with testimonials one at a time. Build as long a sequence of testimonials as you can, and that still convert – don’t limit yourself to just one or two.