You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rand_test.rs
    path of file: ./repos/webrtc/ice/src/rand
    
    the code of the file until where you have to start completion: use std::sync::Arc;

use tokio::sync::Mutex;
use waitgroup::WaitGroup;

use super::*;

    
async fn test_random_generator_collision() -> Result<()> {
    let test_cases = vec![
        (
            "CandidateID",
            0, /*||-> String {
                   generate_cand_id()
               },*/
        ),
        (
            "PWD", 1, /*||-> String {
                  generate_pwd()
              },*/
        ),
        (
            "Ufrag", 2, /*|| ->String {
                  generate_ufrag()
              },*/
        ),
    ];

    const N: usize = 10;
    const ITERATION: usize = 10;

    for (name, test_case) in test_cases {
        for _ in 0..ITERATION {
            let rands = Arc::new(Mutex::new(vec![]));

            // Create a new wait group.
            let wg = WaitGroup::new();

            for _ in 0..N {
                let w = wg.worker();
                let rs = Arc::clone(&rands);

                tokio::spawn(async move {
                    let _d = w;

                    let s = if test_case == 0 {
                        generate_cand_id()
                    } else if test_case == 1 {
                        generate_pwd()
                    } else {
                        generate_ufrag()
                    };

                    let mut r = rs.lock().await;
                    r.push(s);
                });
            }
            wg.wait().await;

            let rs = rands.lock().await;
            assert_eq!(rs.len(), N, "{name} Failed to generate randoms");

            for i in 0..N {
                for j in i + 1..N {
                    assert_ne!(
                        rs[i], rs[j],
                        "{}: generateRandString caused collision: {} == {}",
                        name, rs[i], rs[j],
                    );
                }
            }
        }
    }

    Ok(())
}