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Which is why I test it in the car.
The reg needs a variable voltage positive signal from the control panel between 3 and 7 volts [ approx.] at the yellow wire in order to trigger the regulators transistor ON . So, this is very easy to check in the car , whereas bench testing is going to require you to get a variable trigger voltage supply.
..and , the quick test for blower WITHOUT the regulator is to simply run a ground wire from the blu wire at the neg side of the blower and see if the blower goes into high speed . This electrically by-passes the regulator control circuit. A 12v test lamp at the red on the motor verifies fuse feed , positive, so by grounding the other side [neg/blu] , you now have 12v direct to blower. A good test here is to take an amp draw , but for a quicky , let it run for a few moments and feel that the motor case does not get hot. If it does , you have binding bearings or bad brushes. The amp reading would be best, but this works in the field when no meters are available.
As you can see .these test are much easier in the car as the wiring circuits and controls are already there to get reading off and to jumper for diagnosis...but removal and bench testing will also accomplish the same , but you are then excluding control panel variable voltage verification.
I just prefer the shortest route.