def test():
l = LinkedList()
l.add_node(10)
l.add_node(3)
l.add_node(7)
l.add_node(9)
# List: base -> 10 -> 3 -> 7 -> 9
l = update_list(l)
# List: base -> 3 -> 9
assert isinstance(l, LinkedList)
assert isinstance(l.base, Node)
assert l.base.value is None
assert l.base.next_node is not None
assert l.count_nodes() == 2
p = l.base.next_node
assert p.value == 3
p = p.next_node
assert p.value == 9
p = p.next_node
assert p is None
def test_count_nodes_empty():
ll = LinkedList()
assert ll.count_nodes() == 0
def test_count_nodes():
ll = LinkedList()
ll.add_node('hello')
ll.add_node(5)
assert ll.count_nodes() == 2