Development mule

Mules are drivable, sometimes pre-production vehicles often years away from realization and coming after a concept car that preceded the design of critical mechanical components.

"[4] Mules using modified existing cars may also be used as a development tool to simulate battery-powered vehicles by incorporating their weight, mass distribution, and suspension to evaluate ride and handling.

[5] Mules may also have advanced chassis and powertrain designs from a prospective vehicle that need testing, which can be effectively concealed in the body and interior of a similarly sized production model.

Ford used a Transit van that was modified with a mid-mounted Jaguar XJ220 engine and it had candy wrappers and tabloids on the dashboard to make it look like a regular work vehicle.

[9] Mules are also used to conceal styling changes and visible telltales of performance alterations in near-production vehicles, receiving varying degrees of camouflage to deceive rival makers and thwart a curious automotive press.