I think what most people state is to test ride before buying it. If you special order a car you still get to test drive it before you pay for it. So if they dont carry your model/size and order it for you then yes you should test ride it before you buy it. However it should be expected that they carry a number of popular models in various sizes. Sure they may not have the top-tier Tarmac but they have the lower tier in your size so you can see if the frame geometry works for you before requesting they order a specific model.