I have something like that but trying to find a good ground is sometimes a PITA!
What do you do on older 2 blade only receptacles that are supposedly protected by a GFCI located elsewhere?
Generally, they will have BX and a metal box with the older systems. I will remove a cover if necessary.
There is an apparent dispute about how to test, with UL saying one thing and the test equipment manufacturers saying another. (I’m not sure what authority UL has to say a test at the site of the outlet is invalid.)
See page 4 of this document: http://www.idealindustries.com/media/pdfs/products/guides/basics_of_branch_circuit_testing.pdf
It says: “This simulated arc meets the present UL guidelines for AFCI testers.”
I plan to err on the side of safety and refer it to a sparky unless I get different info from Ideal.
Here we have a bit of BX only; mostly ungrounded Romex style here after K&T/before the grounded wire of the late 1950’s-early 60’s.
No need to remove the cover … if it’s BX and a metal box just use a 3-2 prong adapter. The receptacle yoke will connect the center faceplate screw to the metal box.
And if ya have an older style 3-2 adapter with the wire, that will also work for checking 3-prong receptacles on older 2-wire BX BCW with GFCI protection located elsewhere, to make sure that outlet that is indicating “open ground” is indeed GFCI protected.
But I agree with others that the correct way to check GCFI/AFCI protected outlets is to push the test button on the receptacle/breaker.
JMO & 2-Nickels … 