def test_length_after_append_and_prepend(self):
ll = LinkedList()
assert ll.length() == 0
# Append and prepend should increase length
ll.append('C')
assert ll.length() == 1
ll.prepend('B')
assert ll.length() == 2
ll.append('D')
assert ll.length() == 3
ll.prepend('A')
assert ll.length() == 4
def test_items_after_append(self):
ll = LinkedList()
assert ll.items() == []
# Append should add new item to tail of list
ll.append('A')
assert ll.items() == ['A']
ll.append('B')
assert ll.items() == ['A', 'B']
ll.append('C')
assert ll.items() == ['A', 'B', 'C']
def test_append(self):
ll = LinkedList()
# Append should always update tail node
ll.append('A')
assert ll.head.data == 'A' # New head
assert ll.tail.data == 'A' # New tail
ll.append('B')
assert ll.head.data == 'A' # Unchanged
assert ll.tail.data == 'B' # New tail
ll.append('C')
assert ll.head.data == 'A' # Unchanged
assert ll.tail.data == 'C' # New tail