Add initial unit tests for calculator.py

Author: markusewalker

python-calculator/README.md

@@ -17,3 +17,8 @@ Additionally, this can be ran from your Python IDE of choice such as PyCharm, ID
 
 See below an image of the script in action:
 ![Image of Calculator](https://github.com/markusewalker/Misc-Python-Scripts/blob/main/python-calculator/calculator.png)
+
+### Testing
+Included is `calculator_unittest.py` to check for correctness. The tests provide few, basic tests to verify the addition, subtraction, multiplication and division functions are working properly. To run in the command-line, run the following command:
+
+**python3 -m unittest calculator_unittest.py**

python-calculator/calculator.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 # Authored By: Markus Walker
-# Date Modified: 1/28/22
+# Date Modified: 1/29/22
 #
 # Descrption: Simple calculator written in Python 3. It provides the following
 # operations:

python-calculator/calculator_unittest.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+
+# Authored By: Markus Walker
+# Date Modified: 1/30/22
+#
+# Descrption: Unit test for the calculator.py script. Several unit tests 
+# against the addition, subtraction, multiplication and division functions
+# of the calculator.py script.
+from calculator import *
+import unittest
+from unittest.mock import patch
+
+class TestCalculator(unittest.TestCase):
+    def test_addition(self):
+        self.assertEqual(addition(20,10), 30.0)
+        self.assertNotEqual(addition(20,10), 10.0)
+    
+    def test_subtraction(self):
+        self.assertEqual(subtraction(20,10), 10.0)
+        self.assertNotEqual(subtraction(20,10), 30.0)
+
+    def test_multiplication(self):
+        self.assertEqual(multiplication(20,10), 200.0)
+        self.assertNotEqual(multiplication(20,10), 2.0)
+
+    def test_division(self):
+        self.assertEqual(division(20,10), 2.0)
+        self.assertNotEqual(division(20,10), 200.0)
+
+if __name__ == "__main__":
+    unittest.main()