It's not only the transmission you will damage.
You will probably destroy the front of the Bongo and remove the wall of the garage test bay!. You will have two driven wheels on the tester and two on dry concrete. result....................... violent forward propulsion!!!
Any 4WD franchise/M.O.T. workshop must have a Tapley. As previously said any 4WD car with permanent drive to all 4 wheels (those mentioned above +Discovery and Range Rover) will have the same problem. Quite a few franchised garages go out side for M.O.T. tests, so ring your local Landy Dealer and ask him who does his M.O.T.'s. Problem should be solved.