Doctests

Doctests are a way to include executable example code within documentation strings, often referred to as docstrings, in programming languages. The primary purpose of doctests is to serve as both documentation and automated tests for code. By embedding examples directly within the docstrings, developers ensure that the examples remain accurate and up-to-date as the code evolves.

The concept originated in the Python programming language but has been adopted or inspired similar features in other languages. In Python, doctests are typically written as interactive Python session examples within the docstring. When a doctest module is run, it searches for these examples, executes them, and compares the output to the expected output provided in the docstring. If the output matches, the test passes. If there is a discrepancy, the test fails, indicating a potential issue with the code or the documentation.

This integration of testing into documentation offers several benefits. It makes the code easier to understand by providing concrete examples of how to use it. It also acts as a form of continuous testing, as these examples are checked regularly, preventing regressions and ensuring that the documentation stays synchronized with the code's behavior. Doctests can be particularly useful for library functions and modules, where clear usage examples are crucial for users.