Don't trust testimonials. Some students are given incentives to give good testimonials. Like discounts on course price, free books ... Well-known trick in the training industry.Video testimonials definitely can't be faked. coughfiver.comcough.
The only thing you can trust is long-term (10 years) track record showing all the past transactions, including all the losers. These trainers selectively show their biggest winners to sell their course. Don't fall into this trick. Look at their losers too, especially their biggest losers. It gives you a clue how they manage their risk.