#[cfg(test)]
pub mod tests {
    // Note this useful idiom: importing names from outer (for mod tests) scope.
    // use super::*;
    // use super::super::*;

    // #[test]
    // fn test_two_sum() {
    //     assert_eq!(main::two_sum(vec![3, 2, 4], 6), vec![1, 2]);
    // }
}