I have been dropping a piece of track on my bench whenever I needed to test something on the rollers for years, so I thought it was finally time to do a real test track. Nothing fancy, I just wanted functional. I had tons of Fastrack laying around, so the track selection was easy, already had the raw materials. I also had some scrap lumber, and 3/4" was the perfect size. It turns out that the rollers raise the locomotive exactly 3/4", so having a step for the tender to set directly on the track works perfectly and allows me to test the locomotive connected with a wireless tether to the tender. The whole assembly is 48" long, the lower section os 30" long, and the upper section is 15" long. That left me 3" on the end for connections.
To avoid ever having to take this apart, all the track segments are joined by soldered #18 jumpers, no sense depending on the rail joints here.
My connections are all made on a piece of Lexan, it so happens I have a lot of that laying around, and it's perfect for this kind of application.
I have three connections and a toggle switch. The red terminal is, obviously, the center rail. The two outer black terminals are the outside rails, they are isolated from each other. The switch allows me to common the outside rails when desired. Having the outside rails isolated allows me to plop a 2-rail locomotive on the rollers for testing. I spaced the terminals for double banana jacks, normally it's just connecting to one outside rail and the center rail with the switch providing the connection to the other rail. For 2-rail testing, I just use discrete banana leads to bring the power to the track.
It's a basic test track, but quite functional. It was also very quick to slap together as I needed to get busy using it. 
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I've seen some pretty lavish test tracks, way more than I need. 
Thanks for the great tip and sharing!
