rowd,
A plug in tester will not test a GFCI that is installed without an EGC. That tester works by placing a resistor between the hot and ground. If there is no ground, then there will be no current flow and the GFCI will not trip. Just use the test button on the GFCI. It works by placing a resistor between the line side hot and the load side neutral. It doesn't need the EGC to function. There is no need to use any type of external tester to test GFCI receptacles.
Don
