Some, but not all. People spending six figures for a toy tend to do a little bit of research and know what they want once they step foot in a certain direction. These are passion driven purchases, not necessities. Viper is a unique breed, people either want one or they do not. It is a pretty polarizing product, not really cross-shopped with a whole lot. Closest in the price range would be a ZR1 Corvette, and even those typically aren't test driven.
I know guys who are on the elusive "Ferrari waiting list" for being long-term Ferrari customers. They get invited to purchase the latest models first. Pretty sure none of them have ever test driven any of their previous (or future) purchases. They simply want what they want. Same goes for Lambo or McLaren purchasers - no prior test drives given (or needed).
I wouldn't compare the Viper to any Porsche 911, not even close. Plus, those Porsche salesmen around here actually earn enough to drive their own Porsche. They KNOW the product inside and out, this is what makes them successful at selling. They own/drive the product. Not the same with Viper salespeople, unless you buy from some of our site Sponsors who sell them. Tomball/ViperExchange, Woodhouse, etc... those stores KNOW Vipers. Support those who support us, when possible.
What it all boils down to, is that the Viper is not a mass-produced car. They build approximately the same number of Corvettes in a single year, than the total amount of Vipers in existence. Lambo has built more Gallardos than Dodge/SRT has built Vipers in the same respective years. People think of the Gallardo as something rare? Not so much.