Free: Contests & Raffles.
I can't imagine anyone actually "testing" different chokes from different companies. That could run into a lot of money just purchasing all the different company's tubes and then using a very extensive test where in you actually count and then average number of shot within a prescribed circle at a given range, etc, etc...but, after all that BS, I can tell you that I did buy a ex-full from Mossberg for a 20 g model 500 and it shoots a great pattern right on line and the price was reasonable.