old_contents: """Tests for double linked list class."""
  
  import pytest
  
  
  @pytest.fixture
  def new_list():
      """Create a new empty double linked list."""
      from doublelinkedlist import DoubleLinkedList
      this_list = DoubleLinkedList()
      return this_list
  
  
  def test_new_node_is_empty():
      """Test a new node is empty."""
      from doublelinkedlist import Node
      new_node = Node()
      assert new_node.data is None
      assert new_node.next_item is None
      assert new_node.prev_item is None
  
  
  def test_new_node_with_data_has_data():
      """A new node with data has data."""
      from doublelinkedlist import Node
      new_node = Node(5)
      assert new_node.data == 5
  
  
  def test_new_node_with_next_has_next():
      """A new node with data and next has next and data."""
      from doublelinkedlist import Node
      node1 = Node(5)
      node3 = Node(1)
      node2 = Node(4, node1, node3)
      assert node2.next_item is node1
      assert node2.prev_item is node3
  
  
  def test_new_doublelist_has_no_head(new_list):
      """A new double linked list is without a head."""
      assert new_list.head is None
      assert new_list.tail is None
  
new_contents: """Tests for double linked list class."""
  
  import pytest
  
  
  @pytest.fixture
  def new_list():
      """Create a new empty double linked list."""
      from doublelinkedlist import DoubleLinkedList
      this_list = DoubleLinkedList()
      return this_list
  
  
  def test_new_node_is_empty():
      """Test a new node is empty."""
      from doublelinkedlist import Node
      new_node = Node()
      assert new_node.data is None
      assert new_node.next_item is None
      assert new_node.prev_item is None
  
  
  def test_new_node_with_data_has_data():
      """A new node with data has data."""
      from doublelinkedlist import Node
      new_node = Node(5)
      assert new_node.data == 5
  
  
  def test_new_node_with_next_has_next():
      """A new node with data and next has next and data."""
      from doublelinkedlist import Node
      node1 = Node(5)
      node3 = Node(1)
      node2 = Node(4, node1, node3)
      assert node2.next_item is node1
      assert node2.prev_item is node3
  
  
  def test_new_doublelist_has_no_head(new_list):
      """A new double linked list is without a head."""
      assert new_list.head is None
      assert new_list.tail is None
  
  
  def test_when_push_list_size_grows(new_list):
      """When I push to my list, the size of the list grows."""
      new_list.push(5)
      assert new_list.size == 1
  
subject: test for when we push the size of the list grows