test_calc_try2.py

import unittest # importing standard unittest module from python library
from testapp.calculator import Calculator # import

class TddPython(unittest.TestCase): # our class that would contain multiple test cases
 
    def test_calc_subtract_method(self): # test method
        calc = Calculator() # initiliate the Calculator
        result = calc.subtract(4,1)
        self.assertEqual(3, result)
      
if __name__ == '__main__':
    unittest.main() # execute test