Mutatis is the proof of concept, I have presented for the Demo Day of the Solana Summer Fellowship 2024. It is the result of ten days of coding. In "work in progress", it still requires many improvements.

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Mutatis Mutandis

Mutatis mutandis is a Medieval Latin phrase meaning "with things changed that should be changed" or "once the necessary changes have been made". (Source : https://en.wikipedia.org/wiki/Mutatis_mutandis)

Mutation testing

Mutation testing is a technique used to evaluate the quality of your unit tests. It involves introducing small changes (mutations) to your code, and then checking if your tests can detect these changes by failing. If a test passes despite a mutation, it indicates that the test suite might not be comprehensive enough.

How it works:

1. Original code: You have a function or a set of functions covered by unit tests.
2. Introduce mutation: Small changes are made to the code (e.g., flipping a boolean, changing an operator).
3. Run tests: The unit tests are executed against the mutated code.
4. Check results:
   • If the tests fail, they "kill" the mutation, meaning the test suite is effective.
   • If the tests pass, the mutation "survives," indicating that the test suite might not cover that part of the code well.

Example:

Here’s a simple code example in Rust:

Original function:

fn is_even(x: u32) -> bool {
    x % 2 == 0
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_is_even() {
        assert_eq!(is_even(4), true);
        assert_eq!(is_even(3), false);
    }
}

Mutated version:

A mutation could be flipping the boolean condition in is_even:

fn is_even(x: u32) -> bool {
    x % 2 != 0  // Changed from `==` to `!=`
}

If the tests fail, the mutation was successfully caught. If they pass, you have a "surviving mutation," indicating that the tests may not be robust enough.

Benefits:

• Helps ensure that your tests are meaningful.
• Encourages stronger, more effective tests.

Mutation testing tools automate this process by applying mutations and running your test suite.

Resources

Mutation testing:

• Mutatis mutandis - Wikipedia
• Mutatis mutandis — Wikipédia
• Mutation Testing - Software Testing - GeeksforGeeks
• Understanding Mutation Testing: A Comprehensive Guide - testRigor AI-Based Automated Testing Tool

Testing tools:

• Increase Solana test speed 10x using Bankrun - YouTube