Day 20: Testing and Test-Driven Development in Python

Test-Driven Development (TDD) is a smart way to develop software. Instead of jumping straight into writing code, TDD suggests writing tests first. It's like planning your work before you start building something. With TDD, you break down your tasks into small, manageable chunks. Each chunk is accompanied by a test that checks if that specific part of the code works as expected.

Once the test is in place, you write the code to make the test pass. This process ensures that your code is focused, reliable, and less likely to have big issues later on. In a nutshell, TDD helps you build better software step by step, ensuring it works well from the start.

Unittest

The unittest module in Python is a built-in framework for writing and running unit tests. It provides a set of classes and methods for creating test cases, organizing tests into test suites, running tests, and reporting the results.

Key components of the unittest module include:

1. TestCase Class: The unittest.TestCase class is the base class for all test cases. Test cases are defined by creating subclasses of Testcase and implementing test methods within them.

2. Test Methods: Test methods are functions within test case classes that start with the prefix test_. These methods contain the individual tests that verify the behavior of specific units or components of the code.

3. Assertions: Assertions are methods provided by the unittest.TestCase class for verifying expected outcomes in test methods. Examples of assertions include assertEqual(), assertTrue(), assertFalse(), assertRaises(), etc.

Overall, the unittest module provides a comprehensive framework for writing and running unit tests in Python, helping developers ensure the correctness and reliability of their code.

Here's an example of testing a Python function

import unittest

def square(x):
    return x * x

#test case class
class TestSquareFunction(unittest.TestCase):

    def test_square(self):       
        result = square(5)
        #assertion
        self.assertEqual(result, 25, "Square calculation is incorrect")

#function to run the tests
if __name__ == '__main__':
    unittest.main()

• A test case class TestSquareFunction is created, inheriting from unittest.TestCase.

• Inside the test case class, we define a test method test_square() where we call the square() function with a sample input (5) and assert that the result is 25, which is the square of 5.

• The unittest.main() function is used to run the tests when the script is executed.