def test_linked_list_delete_head():
new_list = SinglyLinkedList()
new_list.addAtHead(4)
new_list.addAtTail(6)
new_list.deleteAtIndex(0)
assert new_list.head.val == 6
assert new_list.tail.val == 6
assert new_list.length == 1
def test_linked_list_delete_middle():
new_list = SinglyLinkedList()
new_list.addAtHead(7)
new_list.addAtHead(2)
new_list.addAtHead(1)
new_list.addAtIndex(3, 0)
new_list.deleteAtIndex(2)
new_list.addAtHead(6)
new_list.addAtTail(4)
assert new_list.head.val == 6
assert new_list.tail.val == 4
assert new_list.length == 4
assert new_list.get(4) == 4
def test_linked_list_one_element_delete_head():
new_list = SinglyLinkedList()
new_list.addAtHead(4)
new_list.deleteAtIndex(1)
assert new_list.length == 1
