Complex sentence: The car then undergoes a series of quality control tests to assess function, fit and finish which takes a total of 5 hours, because the car has no emissions these test can be done inside the factory.
Split into simpler sentences: The car then undergoes a series of quality control tests to assess function, fit and finish. The testing processes take a total of 5 hours, because the car has no emissions these test can be done inside the factory.