Added multiplication functionality and a test for it

src/main/py/primitive_calculations.py

@@ -4,3 +4,7 @@ def add(first_number, second_number):
 
 def subract(first_number, second_number):
     return second_number - first_number
+
+
+def multiply(first_number, second_number):
+    return first_number * second_number

src/test/py/test_primitive_calculations.py

@@ -27,6 +27,9 @@ class primitive_calculations(unittest.TestCase):
     def test_subtract_minus_5_minus_minus_5_equals_0(self):
         self.assertEqual(subract(-5, -5), 0)
 
+    def test_subtract_minus_5_minus_minus_5_equals_1(self):
+        self.assertEqual(multiply(5, 5), 25)
+
 
 if __name__ == "__main__":
     unittest.main()