Example of Unit Testing.

calculation.py

import time

class Calc:
    """ Arithmetic Operations for two numbers, per function. """
    
    def add(self, n1, n2):
        """ Performs addition of two numbers. """
        time.sleep(5) # intentional sleep for measuring time consumed
        return n1 + n2
      
    def sub(self, n1, n2):
        """ Performs subtraction of two numbers. """
        return n1 - n2
      
    def mult(self, n1, n2):
        """ Performs multiplication of two numbers. """
        return n1 * n2
      
    def div(self, n1, n2):
        """ Performs division of two numbers. """
        return n1 // n2
      

calculation_test.py

import calculation
import unittest

calc = calculation.Calc()

class Probe(unittest.TestCase):
    """ Probe for testing Calc class and its methods. """
    
    def test_add(self):
        """ Testing add() method from Calc class. """
        self.assertEqual(calc.add(3, 3), 6)
        
    def test_sub(self):
        """ Testing sub() method from Calc class. """
        self.assertEqual(calc.sub(3, 3), 0)
        
    def test_mult(self):
        """ Testing mult() method from Calc class. """
        self.assertEqual(calc.mult(3, 3), 9)
        
    def test_div(self):
        """ Testing div() method from Calc class. """
        self.assertEqual(calc.div(3, 3), 1)
        
if __name__ == "__main__":
    unittest.main()