#[test]
fn test_vanilla_leap_year() {
    assert_eq!(leap::is_leap_year(1996), true);
}

#[test]
fn test_any_old_year() {
    assert_eq!(leap::is_leap_year(1997), false);
}

#[test]
fn test_century() {
    assert_eq!(leap::is_leap_year(1900), false);
}

#[test]
fn test_exceptional_centuries() {
    assert_eq!(leap::is_leap_year(2000), true);
    assert_eq!(leap::is_leap_year(2400), true);
}

fn main() {
    leap::is_leap_year(0);
}

mod leap {

    pub fn is_leap_year(year:u16) -> bool {
        if year % 4 == 0 {
            if year % 100 == 0  {
                if year % 400 == 0 {
                    true
                } else {
                    false
                }
            } else {
                true
            }
        } else {
            false
        }
    }
}