I did an inspection this afternoon in which two GFCI outlets did not trip when I pressed the button on my GFCI tester, and it turned out their polarity was reversed. They were grounded, and the ground wire was correctly connected. They did turn off when I pressed their “test” buttons.
I have noticed that my tester does not work for non-grounded GFCIs, also. So I test those for GFCI functionality by pressing their “test” buttons.
While it would seem that GFCI function would not be polarity sensitive, I want to make sure before I make an incorrect call. Is it just the way the tester is designed (shorting hot to ground), or does reversal of the hot and “neutral” wires affect the GFCI function?