Tests with Result

Write tests that return Result.

Difficulty

Intermediate

Code

rust

fn parse_number(s: &str) -> Result<i32, std::num::ParseIntError> {
    s.parse::<i32>()
}

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

    #[test]
    fn test_parse_valid() -> Result<(), String> {
        let n = parse_number("42").map_err(|e| e.to_string())?;
        if n != 42 {
            return Err(format!("expected 42, got {}", n));
        }
        Ok(())
    }

    #[test]
    fn test_parse_invalid() {
        assert!(parse_number("abc").is_err());
    }

    #[test]
    fn test_parse_negative() {
        let n = parse_number("-5").unwrap();
        assert_eq!(n, -5);
    }
}

fn main() {
    println!("Run with: cargo test");
}

Explanation

Tests can return Result<(), E> for cleaner error handling.

Key Concepts

Read the code carefully and understand the data flow
Try modifying the example to see how it changes behavior
Run this code in the Rust Playground

Tests with Result

Tests with Result

Difficulty

Code

Explanation

Key Concepts

Related Topics

More Testing Examples

Test Organization

Unit Tests