Series 19: Testing Your Python Applications

Automated tests document intent, ship refactors confidently, and keep CI honest. This series follows the syllabus in article-plan.md: why tests exist, unittest in depth, pytest ergonomies (markers, fixtures, parametrization), pragmatic TDD, unittest.mock isolation, coverage measurement, plus API-level assertions that reuse your FastAPI knowledge.

Articles

• 145. The importance of testing: unit, integration, and end-to-end tests
• 146. Introduction to unittest (Part 1): Writing basic test cases
• 147. Introduction to unittest (Part 2): Assertions, test discovery, and running tests
• 148. Introduction to pytest (Part 1): Basic tests and markers
• 149. Introduction to pytest (Part 2): Fixtures, parameterized tests, and API clients
• 150. Test-driven development (TDD): Basic principles
• 151. Mocking in tests using unittest.mock
• 152. Code coverage — measuring test effectiveness