If you want to quickly and easily confirm proper coil polarity, you need one of these:
https://www.brattons.com/ignition-sp...il-tester.html
It's a nice item for a club to own in their tool kit, because you don't need to use it often. So you can share it around the club as needed.
When you are using a test light, as you describe, the points must be open or you must insert a little non-conductive piece of something between the points. A business card corner works well. If the points are closed, you get false readings.