Writing Tests in Rust

From the Rust cheat sheet · Testing · verified Jul 2026

Writing Tests

Unit tests, integration tests, and test organization.

rust

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

    #[test]
    fn it_works() {
        assert_eq!(add(2, 3), 5);
    }

    #[test]
    #[should_panic(expected = "divide by zero")]
    fn panics_on_zero() {
        divide(1, 0);
    }
}

// Run: cargo test

💡 #[cfg(test)] ensures test code is never compiled into your release binary

⚡ Tests that return Result<(), E> let you use ? instead of .unwrap() — cleaner test code

📌 Use -- --nocapture to see println! output from passing tests

🟢 Integration tests go in tests/ directory and can only access your public API

testingassertunit-tests

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