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: kcp_test.go
    path of file: ./repos/Xray-core/transport/internet/kcp
    
    the code of the file until where you have to start completion: package kcp_test

import (
	"context"
	"crypto/rand"
	"io"
	"testing"
	"time"

	"github.com/google/go-cmp/cmp"
	"github.com/xtls/xray-core/common"
	"github.com/xtls/xray-core/common/errors"
	"github.com/xtls/xray-core/common/net"
	"github.com/xtls/xray-core/transport/internet"
	. "github.com/xtls/xray-core/transport/internet/kcp"
	"github.com/xtls/xray-core/transport/internet/stat"
	"golang.org/x/sync/errgroup"
)

func TestDialAndListen(t *testing.T) {
	listerner, err := NewListener(context.Background(), net.LocalHostIP, net.Port(0), &internet.MemoryStreamConfig{
		ProtocolName:     "mkcp",
		ProtocolSettings: &Config{},
	}, func(conn stat.Connection) {
		go func(c stat.Connection) {
			payload := make([]byte, 4096)
			for {
				nBytes, err := c.Read(payload)
				if err != nil {
					break
				}
				for idx, b := range payload[:nBytes] {
					payload[idx] = b ^ 'c'
				}
				c.Write(payload[:nBytes])
			}
			c.Close()
		}(conn)
	})
	common.Must(err)
	defer listerner.Close()

	port := net.Port(listerner.Addr().(*net.UDPAddr).Port)

	var errg errgroup.Group
	for i := 0; i < 10; i++ {
		errg.Go(func() error {
			clientConn, err := DialKCP(context.Background(), net.UDPDestination(net.LocalHostIP, port), &internet.MemoryStreamConfig{
				ProtocolName:     "mkcp",
				ProtocolSettings: &Config{},
			})
			if err != nil {
				return err
			}
			defer clientConn.Close()

			clientSend := make([]byte, 1024*1024)
			rand.Read(clientSend)
			go clientC
    
func TestDialAndListen(t *testing.T) {
	listerner, err := NewListener(context.Background(), net.LocalHostIP, net.Port(0), &internet.MemoryStreamConfig{
		ProtocolName:     "mkcp",
		ProtocolSettings: &Config{},
	}, func(conn stat.Connection) {
		go func(c stat.Connection) {
			payload := make([]byte, 4096)
			for {
				nBytes, err := c.Read(payload)
				if err != nil {
					break
				}
				for idx, b := range payload[:nBytes] {
					payload[idx] = b ^ 'c'
				}
				c.Write(payload[:nBytes])
			}
			c.Close()
		}(conn)
	})
	common.Must(err)
	defer listerner.Close()

	port := net.Port(listerner.Addr().(*net.UDPAddr).Port)

	var errg errgroup.Group
	for i := 0; i < 10; i++ {
		errg.Go(func() error {
			clientConn, err := DialKCP(context.Background(), net.UDPDestination(net.LocalHostIP, port), &internet.MemoryStreamConfig{
				ProtocolName:     "mkcp",
				ProtocolSettings: &Config{},
			})
			if err != nil {
				return err
			}
			defer clientConn.Close()

			clientSend := make([]byte, 1024*1024)
			rand.Read(clientSend)
			go clientConn.Write(clientSend)

			clientReceived := make([]byte, 1024*1024)
			common.Must2(io.ReadFull(clientConn, clientReceived))

			clientExpected := make([]byte, 1024*1024)
			for idx, b := range clientSend {
				clientExpected[idx] = b ^ 'c'
			}
			if r := cmp.Diff(clientReceived, clientExpected); r != "" {
				return errors.New(r)
			}
			return nil
		})
	}

	if err := errg.Wait(); err != nil {
		t.Fatal(err)
	}

	for i := 0; i < 60 && listerner.ActiveConnections() > 0; i++ {
		time.Sleep(500 * time.Millisecond)
	}
	if v := listerner.ActiveConnections(); v != 0 {
		t.Error("active connections: ", v)
	}
}