1pub fn add(left: usize, right: usize) -> usize {
 2    left + right
 3}
 4
 5#[cfg(test)]
 6mod tests {
 7    use super::*;
 8
 9    #[test]
10    fn it_works() {
11        let result = add(2, 2);
12        assert_eq!(result, 4);
13    }
14}