You can't easily test the advance/retard on the ignition module - only when the bike is running and with a strobe light.
We have a dedicated test rig that can check the advance function and other parameters, over a wide range of rpm.
The self-test function checks for sparks (also confirming battery, connections, coils/leads/caps/plugs are good), but it is not a 100% perfect test for the module.
Very rarely a module will pass the self-test but the low speed operation and/or advance could be 'off'.
This can happen when (for example) the bike has a bad or missing engine ground, and sparks can jump where they shouldn't - for example inside the points housing and into the module via the trigger wires.
This can damage the module internal components.
Unfortunately the grounding issue is not uncommon with the Commando, due to the engine mounting method.
The Sure Fire system can be run with or without resistor caps/plugs, as it is not especially susceptible to radio frequency interference (r.f.i.).
If you have other electronic items on the bike (e.g. electronic tacho, intercom, alarm, etc.), these may be affected by r.f.i. if there is insufficient suppression in the high tension circuits.
So in those cases you may need to fit resistor caps or resistor plugs.
If you are using resistor caps we would normally advise using non-resistor plugs.
Similarly if you are using resistor plugs we would advise using non-resistor caps.
Too much resistance can reduce the available spark energy (although the reduction is usually quite small).
Also, we always recommend using copper cored plug leads with all of our systems.