It can take a while to get through the paperwork. Why would you want to test drive the car, its brand new? It is YOUR car, your lease car.
They will only allow you to drive it away, once you are added to its insurance etc.
But just make sure its the spec you ordered. They should go through the steps of linking your phone to the car and ensure all is well before entering the PIN.
The motability person is there to help you. Its not a shonky 2nd hand car dealer, or a rip off merchant.
Then drive away.