Any way to test the rectifier while it's off the bike?

[cubantunr]

Ok so I have a 93 seca 2, xj600. And I had the bike all running perfect for a bit until last week drove it and it died about 40 min into driving. Took it home and popped out spark plugs they're black. Took bike to a know dealer and they said the carbs are all good but the battery won't stay charging (low volts not enough spark=flooding). I believe they said it's holding 12.2 volts at 5k rpm. So I took the bike home and tested the stator, all turned out good .4 ohms all 3 pins this leads me to believe the rectifier is my culprit. Now I'm wondering is there a way to test the rectifier while off the bike? I don't want to throw it all back together and risk harming the bike just to troubleshoot. Any help is appreciated thanks.