Last time I bought a bike (touring bike), the sales folks were amazed at how long I was riding each bike. It was only 2-3 miles, but the shop was near a nice residential area with hills, flats, straight and curved roads, so I wrung each one out. I didn't buy the one I went there to buy, because another one just felt better.
Mike J. has a good write-up on what to expect and what to look for during a test ride. Check out:
How to evaluate a road bike on a test ride | Almost-Daily Diary