new_contents: """Tests for linked_list.py."""
  
  import pytest
  
  
  @pytest.fixture
  def sample_linked_list():
      """Create testing linked list."""
      from linked_list import LinkedList
      one_llist = LinkedList([1])
      empty_llist = LinkedList()
      new_llist = LinkedList([1, 2, 3, 4, 5])
      return (one_llist, empty_llist, new_llist)
  
  
  def test_node_init():
      """Test node class init."""
      from linked_list import Node
      new_node = Node(0, None)
      assert new_node.contents == 0 and new_node.next_node is None
  
  
  def test_linkedlist_init_empty_size():
      """Test for empty LinkedList init."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert empty_llist.length == 0
  
  
  def test_linkedlist_init_empty_head():
      """Test head in empty LinkedList init."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert empty_llist.head_node is None
  
  
  def test_linkedlist_init_one_size():
      """Test for LinkedList init single item."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert one_llist.length == 1
  
  
  def test_linkedlist_init_one_head():
      """Test head in LinkedList init single item."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert one_llist.head_node.contents == 1
  
  
  def test_linkedlist_init_list_size():
      """Test for LinkedList init with list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.length == 5
  
  
  def test_linkedlist_init_list_head():
      """Test head in LinkedList init with list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.head_node.contents == 5
  
  
  def test_linkedlist_push_size():
      """Test for LinkedList size after push."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      new_llist.push("new")
      assert new_llist.length == 6
  
  
  def test_linkedlist_push_val():
      """Test for LinkedList head value after push."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      new_llist.push("new")
      assert new_llist.head_node.contents == "new"
  
  
  def test_linkedlist_pop_one():
      """Test for Linked List pop on list with one item."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert one_llist.pop() == 1
  
  
  def test_linkedlist_pop_list():
      """Test for Linked List pop on multi-item list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.pop() == 5
  
  
  def test_linkedlist_search_list():
      """Test for LinkedList search list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.search(2).contents == 2
  
  
  def test_linkedlist_search_empty():
      """Test for LinkedList search empty list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert empty_llist.search(2) is None
  
  
  def test_linkedlist_search_list_false():
      """Test for LinkedList search list when search value is not in list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.search(100) is None
  
  
  def test_linkedlist_remove():
      """Test LinkedList remove() on a list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      new_llist.remove(new_llist.search(3))
      assert new_llist.search(3) is None
      assert new_llist.search(4).next_node.contents == 2
  
  
  def test_linkedlist_remove_head():
      """Test LinkedList remove() the head on a list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      new_llist.remove(new_llist.search(5))
      assert new_llist.head_node.contents == 4
  
  
  def test_linkedlist_remove_empty():
      """Test LinkedList remove() on a list list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      with pytest.raises(ValueError):
          new_llist.remove(new_llist.search(100))
  
  
  def test_linkedlist_display():
      """Test for LinkedList display."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert new_llist.display() == (5, 4, 3, 2, 1)
  
  
  def test_linkedlist_display_one():
      """Test for LinkedList display on single item list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert one_llist.display() == (1,)
  
  
  def test_linkedlist_display_empty():
      """Test for LinkedList display on empty list."""
      one_llist, empty_llist, new_llist = sample_linked_list()
      assert empty_llist.display() is None
subject: test for linked list