def test_AnimalShelter_dequeue_pref_dog():
shelter = AnimalShelter()
cheeto = Cat('Cheeto')
oliver = Dog('Oliver')
shelter.enqueue(cheeto)
shelter.enqueue(oliver)
actual = shelter.dequeue('dog')
expected = 'cat'
assert actual == expected
def test_AnimalShelter_dequeue_pref_not_catOrDog():
shelter = AnimalShelter()
cheeto = Cat('Cheeto')
oliver = Dog('Oliver')
shelter.enqueue(cheeto)
shelter.enqueue(oliver)
actual = shelter.dequeue('bird')
expected = None
assert actual == expected