What is the proper type of meter for testing a GCFI receptacle?

Any electrical meter which measures volts or a standard plug tester. (the ones which plug into the receptacle and light up indicator lights) As long as the receptacle measures 110-120V between the hot and neutral, and measures 110-120V between the hot and ground, then it is wired correctly and supplying correct voltage with ground reference. To determine if the GFCI is "tripping" or opening the circuit when it should, simply press the test button. If it doesn't trip, (or reset correctly with the reset button) replace the device.