How to test your adaptor?
I would use a multimeter set to AC Volts - most people don't have one but Amazon ($3) or Radio Shack will sell you one very cheaply. Alternatively a very low wattage 12V auto bulb and a couple of bits of wire to see if anything is coming out of the transformer.
Adaptors often fail if the user needs to coil up the wire on a regular basis - the conductors in the cable can stretch and ultimately break where there's a tight bend in the wire - if you coil up your adaptor cable you might consider this as a potential problem.
Small appliance power adaptors often run slightly warm - if they're at room temperature they're probably dead.
Good luck...
Peccavi
July 2013