1  pub fn add(left: u64, right: u64) -> u64 {
 2      left + right
 3  }
 4  
 5  #[cfg(test)]
 6  mod tests {
 7      use super::*;
 8  
 9      #[test]
10      fn it_works() {
11          let result = add(2, 2);
12          assert_eq!(result, 4);
13      }
14  }