def test_head_tail(self):
single_list = SingleList([])
assert single_list.head is None
assert single_list.tail is None
node1 = Node(1)
single_list.add_last(node1)
assert single_list.head is node1
assert single_list.tail is node1
single_list.pop()
assert single_list.head is None
assert single_list.tail is None
node2 = Node(2)
single_list.add_first(node1)
single_list.add_last(node2)
assert single_list.head is node1
assert single_list.tail is node2
single_list = SingleList([1, 2, 3])
assert single_list.head.val is 1
assert single_list.tail.val is 3
single_list += SingleList([4, 5, 6])
assert single_list.head.val is 1
assert single_list.tail.val is 6
single_list += SingleList([])
assert single_list.head.val is 1
assert single_list.tail.val is 6
def test_add_first(self):
single_list = SingleList([])
with pytest.raises(TypeError):
single_list.add_first(1)
single_list.add_first(Node(1))
assert single_list == SingleList([1])
single_list.add_first(Node(2))
assert single_list == SingleList([2, 1])
assert len(single_list) == 2
