rustlings/exercises/12_options/options1.rs

// This function returns how much icecream there is left in the fridge.
// If it's before 10PM, there's 5 scoops left. At 10PM, someone eats it
// all, so there'll be no more left :(
fn maybe_icecream(time_of_day: u16) -> Option<u16> {
    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
    // value of 0. The Option output should gracefully handle cases where
    // time_of_day > 23.
    // TODO: Complete the function body - remember to return an Option!
    ???
}

fn main() {
    // You can optionally experiment here.
}

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

    #[test]
    fn check_icecream() {
        assert_eq!(maybe_icecream(0), Some(5));
        assert_eq!(maybe_icecream(9), Some(5));
        assert_eq!(maybe_icecream(18), Some(5));
        assert_eq!(maybe_icecream(22), Some(0));
        assert_eq!(maybe_icecream(23), Some(0));
        assert_eq!(maybe_icecream(25), None);
    }

    #[test]
    fn raw_value() {
        // TODO: Fix this test. How do you get at the value contained in the
        // Option?
        let icecreams = maybe_icecream(12);
        assert_eq!(icecreams, 5);
    }
}