old_contents: import unittest
  from calculator import Calculator
  
  class TestCalculator(unittest.TestCase):
  
    def setUp(self):
        self.calc = Calculator()
  
    def test_add_two_numbers(self):
        self.assertEqual(self.calc.calculate("2+2"), 4, "Should equal 4")
  
    def test_subtract(self):
        self.assertEqual(self.calc.calculate("4-1"), 3, "Should equal 3")
  
    def test_add_and_subtract(self):
        self.assertEqual(self.calc.calculate("4+3-1"), 6, "Should equal 6")
  
    def test_calculate_with_spaces(self):
        self.assertEqual(self.calc.calculate("4 - 3   +1"), 2, "Should equal 2")
  
    def test_raise_exception_when_unmatching_subtraction_operand(self):
        with self.assertRaises(RuntimeError) as ex:
            self.calc.calculate("3+2-")
  
        self.assertEqual(ex.exception.message, "Subtraction requires 2 operands")
  
    def test_raise_exception_when_unmatching_addition_operand(self):
        with self.assertRaises(RuntimeError) as ex:
            self.calc.calculate("3-2+")
  
        self.assertEqual(ex.exception.message, "Addition requires 2 operands")
  
  if __name__ == '__main__':
      unittest.main()
  
new_contents: import unittest
  from calculator import Calculator
  
  class TestCalculator(unittest.TestCase):
  
    def setUp(self):
        self.calc = Calculator()
  
    def test_add_two_numbers(self):
        self.assertEqual(self.calc.calculate("2+2"), 4, "Should equal 4")
  
    def test_subtract(self):
        self.assertEqual(self.calc.calculate("4-1"), 3, "Should equal 3")
  
    def test_add_and_subtract(self):
        self.assertEqual(self.calc.calculate("4+3-1"), 6, "Should equal 6")
  
    def test_calculate_with_spaces(self):
        self.assertEqual(self.calc.calculate("4 - 3   +1"), 2, "Should equal 2")
  
    def test_raise_exception_when_unmatching_subtraction_operand(self):
        with self.assertRaises(RuntimeError) as ex:
            self.calc.calculate("3+2-")
  
        self.assertEqual(ex.exception.message, "Subtraction requires 2 operands")
  
    def test_raise_exception_when_unmatching_addition_operand(self):
        with self.assertRaises(RuntimeError) as ex:
            self.calc.calculate("3-2+")
  
        self.assertEqual(ex.exception.message, "Addition requires 2 operands")
  
    def test_calculate_with_one_operand(self):
        self.assertEqual(self.calc.calculate("5"), 5, "Should equal 5")
  
    def test_calculate_with_missing_operator(self):
        with self.assertRaises(RuntimeError) as ex:
            self.calc.calculate("2 5")
  
        self.assertEqual(ex.exception.message, "Input has too many values")
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add test cases for missing operators/operands