A volt meter on the cable between your Dir pin and a ground pin will show if its passing the signal when you reverse an axis, you will get approx 5 volts one way and 0v the other. Similarly with the Step pins but you will only see a small voltage change which will be dependant whether you have active High or Low selected. In other words as you jog you may see the 5v drop slightly or you may see the voltage increase a bit from 0V, the faster you jog the more change you will see.
First thing though would be to check your cable is a straight through and not cross over, just use the Ohm meter on your DVM to check continuity pin to pin on the cable.
Hood