A switch with 2 pins is a SPST switch (single pole single throw). You test for open and closed contacts.
A 3-pin switch is SPDT switch (single pole double throw). The terminals are labelled NO-COM-NC (normally open - common - normally closed).
You test for continuity from COM to NO or NC depending on the state of the switch.

A 3-pin switch is SPDT switch (single pole double throw). The terminals are labelled NO-COM-NC (normally open - common - normally closed).
You test for continuity from COM to NO or NC depending on the state of the switch.
