There are several tests that can be done on the solenoid.
First is a continunity test.. Disconnect wires, use ohm-meter, alas I do not know the proper reading but open circuit = failed,, So do some other readings. but I'm nto sure what is correct.
The "EAR" test.. have your partner switch it to GAS (This works best if it's warm) LISTEN, you should hear both the CLICK of the solenoid and the SNAP of the ignighter (And see the sparks but do not spend a lot of time looking at those)
Other tests are more dangerous and thus I hesitate to suggest them.