I agree with NinerBiker statement "Do the math, do the deal, do the camping. It's gonna drive how it drives, you either change to a better TT suitable to your vehicle, or you change your vehicle to match your new TT." I will add one more thing, load your TT accordingly to stable the load (sway), 10 - 15% of trailer weight.
Taking a test drive? Agree with most here, a worthless test due to many of the comments on the thread, if the numbers work out you can stable the load by correctly loading the TT, if they are to close you are buying the wrong TT to start with. Also do you know many people scrape their first tow and since your asking for a test drive means you are new, or you are at the limits of your TV or skill level for that trailer. Turning corners or backing up correctly... I would never allow it, personal or if I was a dealer.