def test_insert(self):
"""
Tests the insert(index, data) method
"""
dll = DoublyLinkedList()
# test out of bounds
self.assertIsNone(dll.insert(-1, 'data'))
self.assertIsNone(dll.insert(1, 'data'))
# test inserting at index zero in open list (should use unshift(data))
dll.insert(0, 'node zero')
self.assertEqual(dll.length, 1)
self.assertEqual(dll.head.data, 'node zero')
dll.clear()
dll.push(0) # index 0
dll.push(1) # index 1
dll.push(2) # index 2
# insert at index 1
expected_list = [0, 'insert one', 1, 2]
self.assertIsInstance(dll.insert(1, 'insert one'), DoublyLinkedList)
self.assertEqual(dll.length, 4)
self.assertEqual(dll.to_list(), expected_list)
# insert at tail, index 4
expected_list = [0, 'insert one', 1, 2, 'insert tail']
self.assertIsInstance(dll.insert(4, 'insert tail'), DoublyLinkedList)
self.assertEqual(dll.length, 5)
self.assertEqual(dll.to_list(), expected_list)
def main():
# Start with empty list
llist = DoublyLinkedList()
# Insert 6. So the list becomes 6->None
llist.append(6)
# Insert 7 at the beginning.
# So linked list becomes 7->6->None
llist.push(7)
# Insert 1 at the beginning.
# So linked list becomes 1->7->6->None
llist.push(1)
# Insert 4 at the end.
# So linked list becomes 1->7->6->4->None
llist.append(4)
# Insert 8, after 7.
# So linked list becomes 1->7->8->6->4->None
llist.insert(llist.head.next, 8)
print('###################')
llist.printList()
# So linked list becomes 1->7->8->2->6->4->None
llist.insertAt(2, 2)
llist.printList()
print('###################')
llist.delete(llist.head)
llist.delete(llist.head.next)
llist.delete(llist.head.next)
llist.printList()
print('###################')
llist.deleteAt(2)
llist.printList()
