rustlings/exercises/quiz3.rs

// quiz3.rs
//
// This quiz tests:
// - Generics
// - Traits
//
// An imaginary magical school has a new report card generation system written
// in Rust! Currently the system only supports creating report cards where the
// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
// school also issues alphabetical grades (A+ -> F-) and needs to be able to
// print both types of report card!
//
// Make the necessary code changes in the struct ReportCard and the impl block
// to support alphabetical report cards. Change the Grade in the second test to
// "A+" to show that your changes allow alphabetical grades.
//
// Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.

pub fn times_two(num: i32) -> i32 {
    num * 2
}

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

    #[test]
    fn returns_twice_of_positive_numbers() {
        assert_eq!(times_two(4), 8);
    }

    #[test]
    fn returns_twice_of_negative_numbers() {
        // TODO write an assert for `times_two(-4)`
        assert_eq!(times_two(-4), -8);
    }
}