def test_dequeue_second():
shelter = AnimalShelter()
shelter.enqueue(Cat())
shelter.enqueue(Dog())
actual = shelter.dequeue('dog')
assert actual == 'dog'
def test_dequeue_no_pref():
shelter = AnimalShelter()
shelter.enqueue(Cat())
shelter.enqueue(Dog())
actual = shelter.dequeue()
assert actual == 'enter cat or dog'
def test_dequeue_first():
shelter = AnimalShelter()
shelter.enqueue(Cat())
shelter.enqueue(Dog())
actual = shelter.dequeue('cat')
assert actual == 'cat'
def test_not_cat_or_dog():
shelter = AnimalShelter()
actual = shelter.enqueue(Cat())
assert actual == None
def test_add_two():
shelter = AnimalShelter()
shelter.enqueue(Cat())
shelter.enqueue(Dog())
assert shelter.head.next.value == 'dog'
def test_add_one():
shelter = AnimalShelter()
shelter.enqueue(Cat())
assert shelter.head.value == 'cat'
def test_create_shelter():
shelter = AnimalShelter()
assert type(shelter) == AnimalShelter