The 2015 Mazda MX-5 has been spotted performance testing at the Nürburgring.

This model appears to be both longer and wider than current-generation MX-5s. The platform of this car will also be shared with the upcoming Alfa Romeo Spider.

A heavily disguised prototype, believed to be testing proportions and technology for both models, was recently caught testing in the US.

Both the MX-5 and the Alfa Romeo Spider will be sold with their own range of engines. Mazda reportedly intends to fit its MX-5 with a new naturally aspirated 1.6-litre SkyActiv engine, which develops around 130bhp, as the staple unit. A diesel engine option is also being considered.

Alfa Romeo, meanwhile, is likely to fit the Spider with its own 1.4-litre TB MultiAir engine, which is currently offered in the Giulietta in 119bhp and 168bhp forms. A higher-capacity 1750TB unit – the same engine as seen in the new Alfa Romeo 4C – is also likely to be used. Power for the range is likely to go from 120bhp through to 237bhp.

A six-speed manual gearbox is likely to be offered as the standard option in both cars, although a paddle-shift six-speed unit could also become available.

Commonality between the two cars is said to be relatively low, at around 40 per cent. A more typical figure for joint-venture projects is 60 per cent.