You want to check the output of the stator directly without inserting a regulator and battery to make a complete charging system.? There is no real easy what to do that, that I know of. It could be done, but it would be involved. You would have to setup dummy loads on the outputs to do it.
But,... you could make some very basic tests using a meter.
Disconnect the 3 pin connector going to your stator. Set your ohm meter on the lowest scale you have. That will most likely be a 200 ohm scale. Connect your meter leads between any 2 of the 3 leads. Your meter reading should be the same for any 2 wires. That is, the same meter reading between wires 1 &2, 1&3,, 2&3.
Now place your ohm meter in a high range. Something like 200K will do. You should read infinity between any wire (of the 3) and frame grd. That is, wire #1 & ground, #2 & Ground, #3 and ground all should read infinity. These findings are not telling you proof 100% positive if it is Good but it is telling you proof 100% if it is bad.
If you pass those 2 tests and the oil smells good, your stator is probably ok.
Others may chime in with a better way.