I had similar problem with charging system and installed simple volt meter with a on/off switch to stop draining battery when not riding. (£10) eBay.well you'll get multiple different answers here. most of which will be "they are always done in pairs" or something to that extent. to my knowledge of electrical circuits, the only safe way to verify you are good to after swapping out the stator is actively monitoring the charging system at all times, as the issue could happen after riding. the only way i can think of is semi-hard wiring a volt meter to the battery and monitoring the charging voltage.... but I'm not 100% sure that will show how much the stator is outputting.
It will show you normal battery voltage and charging voltage during ride.