// This function returns how much icecream there is left in the fridge. // If it's before 22:00 (24-hour system), then 5 scoops are left. At 22:00, // someone eats it all, so no icecream is left (value 0). Return `None` if // `hour_of_day` is higher than 23. fn maybe_icecream(hour_of_day: u16) -> Option<u16> { match hour_of_day { 0..=21 => Some(5), 22..=23 => Some(0), _ => None, } } fn main() { // You can optionally experiment here. } #[cfg(test)] mod tests { use super::*; #[test] fn raw_value() { // Using `unwrap` is fine in a test. let icecreams = maybe_icecream(12).unwrap(); assert_eq!(icecreams, 5); } #[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(24), None); assert_eq!(maybe_icecream(25), None); } }