Turns out making a street-legal hypercar with a Formula One race car's powertrain isn't easy.

On Tuesday, Mercedes-AMG said the One hypercar's powertrain has completed its static testing in the lab and is moving to the next stage: track testing.

Pre-production Ones are now testing at AMG's proving grounds in Immendingen, Germany. "This is the first dynamic testing of the final calibration of more than 1,000 horsepower," Mercedes-AMG spokesman Barron Smith told Motor Authority.

Mercedes-AMG One prototype

Mercedes-AMG One prototype

Next, pre-production Ones will endure testing on the Nürburgring Nordschleife. Development will be focused on the active aerodynamics. The One features air outlets in the front fenders, active louvers on the front fenders, and a massive rear spoiler, all of which will need to work in harmony.

In addition to the final powertrain calibration, the pre-production Ones now sound as they will in production form.

Unveiled at the 2017 Frankfurt International Motor Show and originally set to go on sale in 2019, the One has been delayed multiple times due to difficulties in getting the powertrain to meet European emissions regulations and withstand the rigors of road duty outside of the racetrack.

Final power output hasn't been disclosed but it's expected to be around 1,020 horsepower. The One is a hybrid with a 1.6-liter turbocharged V-6 that can rev to 11,000 rpm. The engine is expected to produce about 750 hp, and the electric-drive system will make up the rest of the total output. Some of the electric portion of the powertrain is the same as used in F1 cars, just like the engine.

Ones will also feature two electric motors on the front axle to create all-wheel drive, which F1 cars do not have. In electric-only mode, the One will be powered solely by the front electric motors, making it a front-wheel-drive hypercar, though AMG estimates range will be approximately 15 miles on a full charge.

The One is set to potentially redefine the street-legal hypercar. In 2018, then-AMG boss Tobias Moers said the new hypercar might be able to beat the outright Nürburgring lap record of 5:19.55 set that year by Porsche's 919 Evo, but it would require some modifications.

Only 275 Ones will be produced, and each is estimated to cost $2.4 million.

Smith confirmed the One is sold out and is set to enter production at the end of the first quarter in 2021.