old_contents: """This module tests the trie implementation."""
  
  import pytest
  
  @pytest.fixture
  def e_trie():
      """Fixture to crate an empty tree."""
      from trie import Trie
      return Trie()
  
  
  def test_create_emtpy_tree(e_trie):
      """Test creating an empty Trie."""
      from trie import Trie
      assert isinstance(e_trie, Trie)
  
  
  def test_insert_single_letter_sets_root(e_trie):
      """Test inserting a single letter word sets root."""
      e_trie.insert('a')
      assert e_trie.root.children['a'].end is True
      assert e_trie.root.children['a'].children == {}
  
  
  def test_insert_word_creates_single_branch(e_trie):
      """Test inserting a single world creates branch as expected."""
      from trie import Node
      e_trie.insert('word')
      assert isinstance(e_trie.root.children['w'], Node)
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].prev is e_trie.root
  
  
  def test_insert_second_word_creates_branch(e_trie):
      """Test inserting second word creates branch off first word."""
      e_trie.insert('word')
      e_trie.insert('worst')
      assert list(e_trie.root.children.keys()) == ['w']
      assert len(e_trie.root.children['w'].children['o'].children['r'].children) == 2
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].children['o'].children['r'].children['s'].children['t'].end is True
new_contents: """This module tests the trie implementation."""
  
  import pytest
  
  
  @pytest.fixture
  def e_trie():
      """Fixture to crate an empty tree."""
      from trie import Trie
      return Trie()
  
  
  def test_create_emtpy_tree(e_trie):
      """Test creating an empty Trie."""
      from trie import Trie
      assert isinstance(e_trie, Trie)
  
  
  def test_insert_single_letter_sets_root(e_trie):
      """Test inserting a single letter word sets root."""
      e_trie.insert('a')
      assert e_trie.root.children['a'].end is True
      assert e_trie.root.children['a'].children == {}
  
  
  def test_insert_word_creates_single_branch(e_trie):
      """Test inserting a single world creates branch as expected."""
      from trie import Node
      e_trie.insert('word')
      assert isinstance(e_trie.root.children['w'], Node)
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].prev is e_trie.root
  
  
  def test_insert_second_word_creates_branch(e_trie):
      """Test inserting second word creates branch off first word."""
      e_trie.insert('word')
      e_trie.insert('worst')
      assert list(e_trie.root.children.keys()) == ['w']
      assert len(e_trie.root.children['w'].children['o'].children['r'].children) == 2
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].children['o'].children['r'].children['s'].children['t'].end is True
  
  
  def test_second_word_no_forks(e_trie):
      """Test inserting a second word with different first letter."""
      e_trie.insert('sword')
      e_trie.insert('word')
      assert len(e_trie.root.children) == 2
      assert e_trie.root.children['w'].prev == e_trie.root
      assert len(e_trie.root.children['s'].children) == 1
      assert len(e_trie.root.children['s'].children['w'].children) == 1
      assert len(e_trie.root.children['s'].children['w'].children['o'].children) == 1
      assert len(e_trie.root.children['s'].children['w'].children['o'].children['r'].children) == 1
  
  
  def test_insert_short_shared_word(e_trie):
      e_trie.insert('wordless')
      e_trie.insert('word')
      assert len(e_trie.root.children) == 1
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].children['l'].children['e'].children['s'].children['s'].end is True
  
  
  def test_insert_long_shared_word(e_trie):
      e_trie.insert('word')
      e_trie.insert('wordless')
      assert len(e_trie.root.children) == 1
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].end is True
      assert e_trie.root.children['w'].children['o'].children['r'].children['d'].children['l'].children['e'].children['s'].children['s'].end is True
  
subject: insert method tested