Yes, we’ve already seen the Cadillac ATS in the flesh and on the stand at the Detroit Auto Show last month, but that until recently, we hadn’t had a chance to see one actually in action. That changed this past weekend, as our Creative Director spotted a 2013 ATS prototype out testing on public roads. The video clearly shows the sport sedan, decked out in full camouflage, testing just outside of Ann Arbor, Michigan. The car is obviously an upcoming model of the ATS, but from the looks of things, it doesn’t carry anything in the way of serious performance modifications. Translation: we’re not convinced this is some sort of ATS-V, especially considering that GM has been tight-lipped about if such a model will exist, and most ATS variants – including a coupe, convertible, and wagon -- have allegedly been postponed. We’d venture the heavy camo at this point is simply an act of omission: even months after the launch of the Buick Regal GS, we still see development cars running about with camouflaged tape and fascias cribbed from the European Opel Insignia OPC. Regardless, we imagine GM’s looking to accumulate as much real-world validation before the car bows later this year. The ATS will initially be offered with three engine options, including a direct-injection, 190-hp, 2.5-liter I-4 (shared with the Chevrolet Malibu); a 270-horsepower, 2.0-liter turbo four cylinder; or Caddy’s ubiquitous 3.6-liter, direct-injected V-6 engine, which should produce about 315 hp. Transmission choices include both a six-speed manual or a six-speed automatic, and buyers can choose between rear-wheel or all-wheel-drive. The 2013 ATS will go on sale this summer, just time to battle against the mighty, redesigned 2012 BMW 3 Series. Thanks to Kelly Ryan Murphy for the video!