def test_insert_empty():
dll = Dll()
dll.insert(500)
assert dll.head.prev is None
assert dll.head.next_node is None
assert dll.head.value == 500
assert dll.head is dll.tail
def test_insert():
dll = Dll()
dll.insert(500)
first_node = dll.head
dll.insert(600)
assert dll.head.next_node is first_node
assert dll.head.prev is None
assert dll.head.value == 600
assert dll.tail.prev is dll.head
def test_remove_tail():
dll = Dll()
dll.insert(500)
dll.insert(600)
dll.insert(700)
dll.remove(500)
assert dll.tail.value == 600
assert dll.tail.prev is dll.head
assert dll.tail.next_node is None
def test_remove():
dll = Dll()
dll.insert(500)
dll.insert(600)
back = dll.head
dll.insert(700)
dll.insert(800)
front = dll.head
dll.insert(900)
dll.remove(700)
assert back.prev is front
assert front.next_node is back
def test_remove_not_found():
dll = Dll()
dll.append(600)
dll.insert(700)
with pytest.raises(LookupError):
dll.remove(500)
