The only way to test them is to hook them up to a D series EFIS or a Skyvew EFIS. It's not hard to test if you have an EFIS, but without one, there is no way to test them. At the same time, the only thing you can really do on the bench is test to see if they are visible on the network. They are required to be calibrated before they can be tested, which requires that they be connected to the controls. I suppose you could fake the control inputs for the calibration on the bench if you wanted to. My recommendation, test fit them to make the control rods and drill the holes for connection then leave the wing servo out until the wing is finished and leave the tail one servo installed and ready for wiring.
I will never understand the number of people that recommend installing the servos in the wing before it is closed up. I have never once done this in probably 30+ auto pilot installations and have never had difficulty installing the servo in a closed up wing. It's much easier on a wing stand, but isn't difficult with the wing installed either. I see way too many people selling servos that they have had for years because they changed their mind about what auto pilot they would be installing.
