babby's breakfast program

food.rs

/// Food, food, food.  I love food.
pub mod food {
    use std::rand::{Rand, Rng};

    /// All food has calories
    pub trait Food {
        fn calories(&self) -> u64;
    }

    /// There are some things you can eat for breakfast.
    pub enum Breakfast {
        Eggs,
        Granola,
        None
    }

    /// Sometimes you don't know what you want for breakfast...
    impl Rand for Breakfast {
        fn rand<R: Rng>(rng: &mut R) -> Breakfast {
            match rng.gen_range(0u, 3u) {
                0u => Eggs,
                1u => Granola,
                _ => None
            }
        }
    }

    /// Breakfast is food, too.
    impl Food for Breakfast {
        fn calories(&self) -> u64 {
            match *self {
                Eggs => 160,
                Granola => 140,
                None => 0
            }
        }
    }

    #[cfg(test)]
    mod test {
        use super::{Breakfast, Granola, Eggs, None, Food};
        use std::rand;
        use std::rand::Rng;

        #[test]
        fn breakfast_calories() {
            assert!(Eggs.calories() > Granola.calories());
            assert!(Eggs.calories() > None.calories());
            assert!(Granola.calories() > None.calories());
        }

        #[test]
        fn random_breakfast() {
            let mut rng = rand::task_rng();
            let breakfast: Breakfast = rng.gen();
            breakfast.calories();
        }
    }
}