def test_delete_at_index(self):
doubly = DoublyLinkedList(
['very first', 'first', 'second', 'third', 'fourth', 'very last'])
self.assertEqual('second', doubly.get_node_by_index_from_top(2).data)
doubly.delete_at_index(2)
self.assertEqual('third', doubly.get_node_by_index_from_top(2).data)
self.assertEqual(
"DoublyLinkedList(['very first', 'first', 'third', 'fourth', 'very last'])",
doubly.__repr__())
self.assertEqual('first',
doubly.get_node_by_index_from_top(2).leftlink.data)
self.assertEqual('third',
doubly.get_node_by_index_from_top(1).rightlink.data)
doubly.delete_from_the_bottom()
doubly.delete_from_the_top()
self.assertEqual("DoublyLinkedList(['first', 'third', 'fourth'])",
doubly.__repr__())
self.assertEqual('fourth', doubly.last_node.data)
self.assertEqual(None, doubly.last_node.rightlink)
self.assertEqual('third', doubly.last_node.leftlink.data)
self.assertEqual('first', doubly.first_node.data)
self.assertEqual(None, doubly.first_node.leftlink)
self.assertEqual('third', doubly.first_node.rightlink.data)
def test_delete_from_one_element_list(self):
doubly = DoublyLinkedList(['first'])
with self.assertRaises(IndexError):
doubly.delete_from_the_bottom()
with self.assertRaises(IndexError):
doubly.delete_from_the_top()
with self.assertRaises(IndexError):
doubly.delete_at_index(1)