If you need to load test it without a drive, you will have to couple it to another motor and run it as an alternator, with a resistive load. Without the load, you could at least check the open-circuit voltage, again with it driven as an alternator.
If you really want to keep it simple, try spinning it with a variable speed electric drill (possibly use a bit of sleeving eg heatshrink to couple the drill to the motor), that will give you the open-circuit emf - best viewed on an oscilloscope to check the waveshape and phase relationships of the output phase voltages. The waveshape could be sinusoidal (a brushless AC motor and more common for a servo application) or more trapezoidal (classic brushless DC motor). If you vary the speed you can plot voltage against output frequency, to give the o/c voltage-speed characteristic. Of course, you ideally need to test against a known good motor.