Don - the resistor heats up and the open circuit shows up, a short would show a lot of smoke and sparks .... usually once a resistor goes it's gone, and it shows up by the engine starting fine, when the resistor is bypassed, and quitting as soon as you let off the starter and coil power needs to come from the resistor
and daddy, bypassing the resistor for a test run will not destroy the points - at worst running a piece of emery a few passes between them will fix up any carboning - the resistor is bypassed and the coil gets full voltage every time you start the engine .... don't understand folks claiming points are trouble, I've always had them on these old rigs and get lots of dependable life out of them, sometimes without even touch ups for long periods
Bill