Although it won't officially debut until the 2013 Frankfurt Auto Show, Porsche
is busy testing prototypes of its upcoming 918 Spyder. Our always-reliable spy photographers have just managed to snap pictures of a 918 test mule doing some hot laps around the Nurburgring
, and it looks delicious in greyscale Martini livery. Unlike the German sportscar builder's previous supercar, the Carrera GT, the 918 Spyder will be a plug-in hybrid.