Measure the battery voltage before and during and after the starter operation.
The starter can draw 120 amps during operation. If the starter is drawing more than that, the battery voltage will drop below 9V and deplete quicker. (A weak battery can also do this, however.)
Knowing this voltage, can also tell you if there is enough voltage to spark the coils.
If the solenoid is limiting current to the starter, bridging the posts will circumvent that problem.
Of course, the best test would be to measure the starter current draw during operation. But, having a 200 or 300 amp meter for personal use is unusual.
A proper battery test will also test it under starting load. Did Autozone do that test?