I think you all knew I would respond to this.
First, the car is checked over when it rolls off the truck, personally, by me, before I sign the release receipt.
Then, I check for codes in the system, and pull it inside. She run to operating temperature, and I check all the fluids. Tire pressures, install locking lug nuts, and retorque all the others, just in case, and check for any fluid leaks, and put on the front air dams.
Then, I install the GM scan tool, scan Every system, and then I have the saleman contact the customer, to confirm that I can take the test drive to verify all functions with a scan tool, before releasing the vehicle to detail.
If they do not, I explain that they will have to take a test drive with me, and my scan tool to verify full function, before I can release the vehicle.
Once on the road, I verify all function, of every single part, radio, windows, locks, remotes, climate control, and every thing else, and only then, do I release the car.
You see, it is called a PDI, which is predelivery inspection, and that is what I do, inspect every aspect of the vehicles before release.
While I can ONLY speak for myself, this is how I do it, and it takes about an hour, and a half.
Best to all, c4c5