Wiper bench test…on car

Guys my wipers don’t work. I have the procedure for bench testing the motor. Is there any reason why I can’t do the bench test with the wiper motor still attached? I’d unplug the bulkhead connection for the wipers and test it on the disconnected battery

this test;
Bench testing procedure.


Test #1(Hi speed)


Connect jumper wire from motor case to battery ground.
Connect second jumper wire from batterypositive to BROWN lead.
Motor should run hi speed continuously.


Test #2 (Lo speed)


Connect jumper wire from motor case to battery ground.
Connect jumper wire from GREEN wire to battery ground.
Join BROWN and RED wires together and connect a jumper wire from battery positive to them.
Motor should run at slower speed.