I know I can press the "test" button on the breaker in the panel.
But I want to double-check that there isn't some strange wiring situation hidden in the walls that could prevent the GFCI from tripping properly. I have used an outlet GFCI tester but it tests by using ground, which I don't have (hence new GFCI breakers).
Theoretically I could test by sticking a fork in the socket, but even if I had a controlled way to do that (e.g. plug with wires tied together and insulated well), I am nervous about a situation like that causing a rapid heat build-up and damaging/melting things, or starting a fire.
One idea I had was to take my GFCI tester and wire it to an outlet so that the tester's ground goes to the outlet neutral. Then pressing the button on the tester would do the normal test, but using hot/neutral. Would that work and be safe?