def test_linked_list_insert_before():
ll = LinkedList()
ll.head = Node(1)
ll.head.next = Node(2)
ll.insert_before(2, 3)
assert ll.head.next.value == 3
assert ll.head.next.next.value == 2
def test_linked_list_insert_after():
ll = LinkedList()
ll.head = Node(1)
ll.head.next = Node(2)
ll.insert_after(1, 4)
assert ll.head.next.value == 4
assert ll.head.next.next.value == 2
def test_linked_list_append():
ll = LinkedList()
ll.head = Node(1)
ll.head.next = Node(2)
ll.append(3)
assert ll.head.next.next.value == 3
assert ll.head.next.next.next == None