"Understanding Unit Testing in Python: Writing Test Cases with unittest for Caesar Cipher"

“unittest” is a Python's built-in testing framework. It helps write and organize test cases to validate that the code behaves as expected.

• We're importing the encryption and decryption functions from the “ceaser.py” module.

    import unittest
    from ceaser import encryption,decryption
  

• “TestCaesarCipher” class defines the test cases and It inherits from unittest.Testcase*, which gives it access to various testing methods. And also provides methods to compare actual and expected outputs.*

    class TestCaesarCipher(unittest.TestCase):
  

• “self.assertEqual” compares two values. If the values are equal, the test passes; if not, the test fails. For example:

  • The string ”hello world” with a shift of 3 should be encrypted to “khoor zruog”.

  • Special characters like commas and spaces remain unchanged (e.g., ”hello, world!” becomes “mjqqt, btwqi!” with a shift of 5)

    def test_encryption(self):
        self.assertEqual(encryption("hello world", 3), "khoor zruog")
        self.assertEqual(encryption("hello, world!", 5), "mjqqt, btwqi!")

    def test_decryption(self):
        self.assertEqual(decryption("khoor zruog", 3), "hello world")
        self.assertEqual(decryption("mjqqt, btwqi!", 5), "hello, world!")

if __name__==”__main__” ensures that allows the code to run tests when we run the script but not when the script is imported as a module.

• unittest.main() method runs all the test cases within the TestCaeserCipher class.

    if __name__ == '__main__':
        unittest.main()
  

  In short, testing ensures that your code behaves as expected, reduces bugs, and helps maintain high code quality over time.