Thermostat Testing New Part Bad?

I tested my termination thermostat in my fridge which I thought was bad in ice water. It did not close or get a reading on the multimeter. I bought a factory new replacement & did the same test, it did not close or show continuity. The thermostat's have a plastic housing. Is it possibly I bought the part and it was bad?
Or do the thermostat's with a plastic housing need to get colder then the metal housing thermostat's?

Any help is appreciated.