new_contents: from bst import BinarySearchTree
  
  
  nodes = [5, 4, 8, 3, 43, 22, 7, 74, 2]
  
  
  def test_insert_nodes():
      """size of tree equal to number of values inserted"""
      b = BinarySearchTree()
      for n in nodes:
          b.insert(n)
      assert b.size() == 9
  
  
  def test_contains_node():
      """expected nodes in tree"""
      b = BinarySearchTree()
      for n in nodes:
          b.insert(n)
      assert b.contains(74)
      assert b.contains(2)
      assert b.contains(5)
      assert b.contains(43)
      assert not b.contains(103)
  
  
  def test_balance():
      """balance updated when node added"""
      b = BinarySearchTree()
      for n in nodes:
          b.insert(n)
      assert b.balance() == 0
      b.insert(90)
      assert b.balance() == -1
  
  
  def test_depth():
      """depth updated as nodes added"""
      b = BinarySearchTree()
      for n in nodes:
          b.insert(n)
      assert b.depth() == 4
      b.insert(90)
      assert b.depth() == 5
  
  
  def test_size():
      """size on empty and when populated"""
      b = BinarySearchTree()
      assert b.size() == 0
      for n in nodes:
          b.insert(n)
      assert b.size() == 9
  
  
  def test_root():
      """check tree's root and child nodes"""
      b = BinarySearchTree()
      for n in nodes:
          b.insert(n)
      assert b.root.val == 5
      assert b.root.left.val == 4
      assert b.root.right.val == 8
  
subject: Add tests for binary search tree