def METHOD_NAME(self):
    fridge_meter = ElecMeter()
    fridge = Appliance({'type':'fridge', 'instance':1})
    fridge_meter.appliances = [fridge]
    mg = MeterGroup([fridge_meter])
    self.assertEqual(mg.select_using_appliances(category='cold'), mg)
    # TODO: make this test more rigorous!