It's a lot less work to get a "no load" test by removing the spark plugs. Bench-running a starter with no load whatsoever determines exactly nothing. A no compression spin will tell you more about the condition of the starter, because it's going to still be spinning the engine, just not fighting compression in the process. You should be able to turn the engine sans plugs pretty easily by pulling on the fan blades unless the cylinder walls are rusty, etc.
Jerry
