Yep, just unplug the IAC valve. Yours seems to be a six-pin stepper unit, so to do a simple bench test you can check the resistance of the two coils inside. Here's how you'd do that for a 97 Montero Sport 3.0, the resistance values given and pin orientation is probably the same for your unit: https://workshop-manuals.com/mitsub...component_tests_and_general_diagnostics/

Some theory of operation and general expected values are in MegaSquirt's manual (interspersed with MS-relevant info): http://www.megamanual.com/ms2/IAC.htm

To fully test it, you'd need to drive the stepper motor and compare to expected values, but that's out of my knowledge. Maybe someone on here knows how to set up a jig?

PS: common failure mode for misbehaving/seized IAC valves is clogging of actuator with oil (e.g. from failed/malfunctioning PCV valve), so removing it and giving it a good cleaning may be helpful. Also, the IAC valve works downstream of the coolant temp sensor. While you're climbing around the engine bay checking sensors, you may want to check that one as well.