Python Doctests: The Complete Guide to Documentation-Driven Testing
· 6 min read
Writing documentation is essential, but code examples in documentation frequently rot over time as codebases evolve. Python's built-in doctest module solves this problem by allowing you to write executable code examples directly inside your docstrings. The system verifies that the actual function output matches your documented example output.
By combining doctest (for living documentation correctness) and pytest (as your primary test runner), you get a symbiotic testing strategy that guarantees your code works and your documentation is always truthful.
This guide covers when to use doctests, how to write them, the various ways to execute them, and how to optimize your developer workflow in VS Code and Gitpod.