Hello Moe,
You don't have to use a test plug. You can use the regular plug for the saw. Remove the transformer (2 screws) and spark plug. Again, as mentioned earlier, you need to run wires (alligator clips on ends work nice) from the 2 contacts that the transformer would touch to the transformer so it contacts the same locations as when its screwed in. Push the plug into the transformer so the head of the plug is contacting properly. Finally, you'll need to run a wire from the plug base (metal threaded area) to a ground on the saw (like the head near where it screws in. Gotta have a ground on the base of your plug! Spin the flywheel and watch the plug gap to see if you get a spark. If not, its time to check wiring connections, faulty stop switch, flywheel gap, and finally component replacement.
Good luck!
Dan