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: mod.rs
    path of file: ./repos/quinn/quinn-proto/src/tests
    
    the code of the file until where you have to start completion: use std::{
    convert::TryInto,
    mem,
    net::{Ipv4Addr, Ipv6Addr, SocketAddr},
    sync::Arc,
    time::{Duration, Instant},
};

use assert_matches::assert_matches;
use bytes::{Bytes, BytesMut};
use hex_literal::hex;
use rand::RngCore;
use ring::hmac;
use rustls::AlertDescription;
use tracing::info;

use super::*;
use crate::{
    cid_generator::{ConnectionIdGenerator, RandomConnectionIdGenerator},
    frame::FrameStruct,
    transport_parameters::TransportParameters,
};
mod util;
use util::*;

#[test]
fn version_negotiate_server() {
    let _guard = subscribe();
    let client_addr = "[::2]:7890".parse().unwrap();
    let mut server = Endpoint::new(
        Default::default(),
        Some(Arc::new(server_config())),
        true,
        None,
    );
    let now = Instant::now();
    let mut buf = BytesMut::with_capacity(server.config().get_max_udp_payload_size() as usize);
    let event = server.handle(
        now,
        client_addr,
        None,
        None,
        // Long-header packet with reserved version number
        hex!("80 0a1a2a3a 04 00000000 04 00000000 00")[..].into(),
        &mut buf,
    );
    let Some(DatagramEvent::Response(Transmit { .. })) = event else {
        panic!("expected a response");
    };

    assert_ne!(buf[0] & 0x80, 0);
    assert_eq!(&b
    
fn ack_frequency_ack_sent_after_reordered_packets_above_threshold() {
    let _guard = subscribe();
    let max_ack_delay = Duration::from_millis(30);
    let (mut pair, client_ch, server_ch) = setup_ack_frequency_test(max_ack_delay);

    // Send a ping
    pair.client_conn_mut(client_ch).ping();
    pair.drive_client();

    // Send and lose two ack-eliciting packets
    pair.time += Duration::from_millis(5);
    pair.mtu = 0;
    for _ in 0..2 {
        pair.client_conn_mut(client_ch).ping();
        pair.drive_client();
    }

    // Restore the default MTU and send another ping, which will arrive earlier than the dropped ones
    pair.mtu = DEFAULT_MTU;
    pair.client_conn_mut(client_ch).ping();
    pair.drive_client();

    // Server: receive first ping, send no ACK
    pair.time += Duration::from_millis(5);
    let server_stats_before = pair.server_conn_mut(server_ch).stats();
    pair.drive_server();
    let server_stats_after = pair.server_conn_mut(server_ch).stats();
    assert_eq!(
        server_stats_after.frame_rx.ping - server_stats_before.frame_rx.ping,
        1
    );
    assert_eq!(
        server_stats_after.frame_tx.acks - server_stats_before.frame_tx.acks,
        0
    );

    // Server: receive remaining ping, send ACK
    pair.time += Duration::from_millis(5);
    let server_stats_before = pair.server_conn_mut(server_ch).stats();
    pair.drive_server();
    let server_stats_after = pair.server_conn_mut(server_ch).stats();
    assert_eq!(
        server_stats_after.frame_rx.ping - server_stats_before.frame_rx.ping,
        1
    );
    assert_eq!(
        server_stats_after.frame_tx.acks - server_stats_before.frame_tx.acks,
        1
    );
}