While there are several tests for the starter on a vehicle, bench testing provides a definitive answer to a car that does not crank. However, before removing the starter from the vehicle, EasyAutoDiagnostics.com recommends eliminating other possible reasons for the car not cranking.
A dead battery does not turn the starter to crank the engine. Diagnosing a battery problem is easy with a multimeter. Most cars use a 12-volt system, so on the volt setting, the meter should read 12.6 volts. If it is less than 12.3 volts, charging the battery sometimes resolves the problem. If the battery does not hold a charge, it is time for a replacement. The meter is also useful in testing the solenoid and ignition switch.
A locked engine or air conditioner compressor also creates problems similar to a bad starter motor. An appropriately sized socket on the crankshaft pulley bolt allows the tester to turn the engine by hand. If it does not turn, removal of the serpentine belt and another attempt to turn the engine determines if the problem is the engine or air conditioner.
After eliminating these issues as potential causes, it's time for bench testing. Most auto parts houses offer free testing for customers.