5. Test Python code

5. How would you test Python code?

Testing Python code can be done in several ways depending on the scope and complexity. Here's a quick overview of common methods:

1. Manual Testing

• Run your script or function manually.
• Print outputs and check if they behave as expected.
• Good for quick checks but not scalable.

2. Using assert Statements

• Insert assert statements in your code to verify assumptions.

• Example:

  def add(a, b):
      return a + b
  
  assert add(2, 3) == 5
  assert add(-1, 1) == 0
  

• If an assertion fails, Python raises an AssertionError.

3. Unit Testing with unittest Module

• Python’s built-in testing framework.

• Write test cases in classes derived from unittest.TestCase.

• Example:

  import unittest
  
  def add(a, b):
      return a + b
  
  class TestAdd(unittest.TestCase):
      def test_add_positive(self):
          self.assertEqual(add(2, 3), 5)
  
      def test_add_negative(self):
          self.assertEqual(add(-1, 1), 0)
  
  if __name__ == "__main__":
      unittest.main()
  

• Run tests via command line or an IDE.

4. Using pytest (Popular Third-Party Framework)

• More concise and feature-rich than unittest.

• Example:

  def add(a, b):
      return a + b
  
  def test_add():
      assert add(2, 3) == 5
      assert add(-1, 1) == 0
  

• Run with pytest command in terminal.

• Supports fixtures, parameterization, and plugins.

5. Integration and Functional Testing

• Test how different parts of your program work together.
• Use tools like unittest, pytest, or specialized frameworks like behave (for BDD).

6. Test Automation

• Use CI/CD pipelines (GitHub Actions, Jenkins) to run tests automatically on code changes.

Summary:

• Start with manual and assert for small scripts.
• Use unittest or pytest for scalable, maintainable testing.
• Automate tests to ensure code quality continuously.