Sometimes even the simplest programs deserve solid testing—especially when you're working in a team or trying to set strong standards for code quality. In this note, we'll take the most basic example—"Hello, World!"—and build out everything around it to demonstrate how doctests can be used effectively, even for something so trivial. The goal is to build intuition for testing, not just solve a toy problem.
Doctest is a module in the Python Standard Library that enables you to write tests within the documentation of your code—typically inside docstrings. These tests look like interactive Python sessions (as if they were run in a Python shell), and the doctest module verifies that the output matches the expected result. While doctests are generally simpler than unit tests written with unittest or pytest, they are powerful for checking that code examples in documentation remain correct over time.
This guide explores the various ways to execute doctests in Python, from running them via the command line to embedding them in code and running them programmatically.
So I’ve been thinking lately about testing strategies again, and one question came up that I kept circling back to: does every function in my Python codebase need to have a doctest?
If you're writing doctests in Python using Gitpod or VS Code, you don’t need much to get started. Python’s built-in doctest module lets you write examples in your function’s docstring using the familiar >>> prompt, and then run those examples as tests. This is great for small, focused functions or when you want your documentation to double as lightweight tests.
Testing Python Apps with Pytest and Doctest: A Symbiotic Approach
How to test an app using both pytest and doctest in a complementary (symbiotic) way: