How do you perform a tug test to check the connection between the tractor and trailer?

1. Release all brakes, accelerate to 20 km/h, and make a hard service brake application
2. With the trailer parking brakes applied and tractor brakes released, gently try to pull forward in a low gear
3. Visually inspect the fifth wheel locking jaws from under the trailer with a flashlight
4. Disconnect the gladhands and pull the tractor forward to see if the trailer stays in place