In England and some states, the line of sight test is used for presence. It requires the testator to have been able to see the witnesses sign the will if he looked. You have to be in line of sight. You can't be in a nearby room or something.
UPC § 2-502(a)(3) does not require that the witnesses sign in the testator's presence at all. It does require them to see the testator's signing or acknowledgment of the will. If the testator has another sign on his behalf, the UPC requires conscious presence.