Rust Documentation Testing

Overview

Documentation testing in Rust allows you to write tests within your code comments, ensuring that examples in your documentation are correct and functional. This practice helps maintain accurate documentation and provides a straightforward way to validate code behavior.

Key Concepts

• Documentation Comments: In Rust, documentation comments are written using /// for single-line comments and //! for module-level comments.
• Code Blocks in Docs: You can include code snippets in your documentation comments using triple backticks (```) or by using the /// syntax for inline code.
• Testable Examples: The examples included in the documentation can be automatically tested to ensure they compile and run as expected.

How to Write Tests in Documentation

1. Use /// for Documentation Comments: Write your comments above the item (like a function or struct) you want to document.
2. Write Examples: Include examples of how to use the function or struct directly in the comments.
3. Use the doc(test) Feature: Rust automatically treats examples in documentation comments as tests when you run cargo test.

Example

Here's a simple example of documentation testing:

/// Adds two numbers together.
///
/// # Examples
///
/// ```
/// let result = add(2, 3);
/// assert_eq!(result, 5);
/// ```
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

Breakdown of the Example

• Documentation Comment: The /// at the beginning introduces documentation for the add function.
• Example Block: The # Examples section shows how to use the function. The block is enclosed with triple backticks, which allows it to be executed as a test.
• Assertions: The assert_eq! macro checks if the output of the add function matches the expected value.

Running the Tests

To run the tests embedded in your documentation, use the following command in your terminal:

cargo test

This command will compile your code and execute the tests found in the documentation comments.

Benefits of Documentation Testing

• Ensures Accuracy: Keeps your examples up-to-date and correct.
• Improves Clarity: Provides clear examples of how to use your code.
• Encourages Testing: Promotes a testing culture by integrating tests into documentation.

By following these practices, you can effectively use documentation testing in Rust to enhance the reliability and clarity of your code.