Add tests

Author: Jinay Shah

tests/test_calculator.py

@@ -1,5 +1,6 @@
 import unittest
-from pgb import add, mul
+
+from pgb import add, mul, pow, sub
 
 
 class TestCalculator(unittest.TestCase):
@@ -13,6 +14,16 @@ def test_mul(self):
         b = 10
         self.assertEqual(mul.mul(a, b), 50)
 
+    def test_sub(self):
+        a = 5
+        b = 10
+        self.assertEqual(sub.sub(a, b), -5)
+
+    def test_pow(self):
+        a = 2
+        b = 10
+        self.assertEqual(pow.pow(a, b), 1024)
+
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     unittest.main()