What happens when using a GFCI Tester on a non-GFCI outlet?
If the outlet, does not have test and reset buttons, it is clearly not a GFCI itself. However, it is possible that another outlet or circuit-breaker in the line before it has been wired to protect that outlet, as well. No harm will be done testing a non-GFCI outlet using the GFCI tester, but if it does trigger an interrupter elsewhere, you'll need to locate that to reset it.

That said, an outdoor outlet definitely should have GFCI protection, whether 'upstream' or intrinsic. If the GFCI tester does not trigger a protection device, a GFCI outlet should be installed ASAP!