def test_evaluate_divide_by_zero(self):
     """
     In case of divide by zero it should return None for that operator node
     """
     input_string_list = ('2 / 0', '1 + (2 / 0)')
     for input_string in input_string_list:
         root_node = build_tree(input_string)
         with self.assertRaises(EvaluationError):
             evaluate(root_node)
 def test_evaluate_non_digit_token(self):
     input_string = 'A + (B * C)'
     root_node = build_tree(input_string)
     with self.assertRaises(EvaluationError):
         evaluate(root_node)
 def test_evaluate(self):
     for input_string_tup in self.input_string_list:
         input_string, expected_result = input_string_tup
         root_node = build_tree(input_string)
         self.assertEqual(evaluate(root_node), expected_result)