haven't seen any starter that requires a less invasive method of checking. +1 on GH comment that you have to bring it down (a dirty job)....mine had worn carbon brushes and the symptom was cranking at a very low speed. one of my desperate attempt was jumpstarted my pickup using a 6sm (truck battery). But if you follow this path make sure that you don't overdo it or else you'll fry the armature.....
one more thing, avoid cranking the starter for greater than 3-5 seconds even if the engine is hard to start....

you may want to connect the batt positive to the starter armature terminal if you're stuck with a failed solenoid....just be cautious for accidental touching of the cables though.