text: import unittest
  
  from src.TDD.application.calculator import Calculator
  
  class TddInPythonExample(unittest.TestCase):
  
      def setUp(self):
          self.calc = Calculator()
  
      def test_calculator_add_method_returns_correct_result(self):
          result = self.calc.add(2, 2)
          self.assertEqual(4, result)
  
      def test_calculator_returns_error_message_if_both_args_not_numbers(self):
          self.assertRaises(ValueError, self.calc.add, 'two', 'three')
  
      def test_calculator_returns_error_message_if_x_arg_not_number(self):
          self.assertRaises(ValueError, self.calc.add, 'two', 3)
  
      def test_calculator_returns_error_message_if_y_arg_not_number(self):
          self.assertRaises(ValueError, self.calc.add, 2, 'three')