So you can test it two ways. But what do you look for in those two tests.

The first test is easy. The test prop should turn at or slightly under the engine mfg's optimum rpm. You're going to need a tach for this until you've got enough experience to tell rpm for your engine by ear. You can actually do that with 2cycle engines. If you're asking such a basic question about props, chances are good you need a tach. If you're using a 4cycle even experienced flyers use a tach.

The flight test is more complex.