I think it might be easier to simply push the button & see if it works.
However, if you really want to test the solenoid without fear of cranking the engine;
Disconnect the starter motor from the solenoid, but leave the battery side connected.
Disconnect both the black and the yellow/red wires from the solenoid.
Supply 12v to the black low tension wire at the solenoid.
Apply a ground connection to the yellow/red wire.
You should hear the solenoid click & you should now measure battery voltage at the vacant solenoid terminal. Or you could now check for continuity across both high tension terminals with your ohm meter.
***This may not be accurate, as you will now be testing with no load applied to the circuit (ie the starter motor)***
Of course this still leaves lots of other stuff unchecked but there you go.
I'd still turn it on & just push the button though.
