def test_constructor():
items = ("duck", 3, [2, 3, 4], object())
dll = DoubleLinkedList(items)
dll2 = DoubleLinkedList()
for i in items[::-1]:
dll2.insert(i)
for i in items:
assert dll.pop() == dll2.pop()
def test_insert():
dll = DoubleLinkedList()
dll.insert(5)
assert dll.pop() == 5
