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: channel_util_test.go
    path of file: ./repos/gleam/util
    
    the code of the file until where you have to start completion: package util

import (
	"bufio"
	"bytes"
	"io"
	"log"
	"testing"
	"time"
)

func TestCopyBuffer(
    
func TestCopyBuffer(t *testing.T) {

	// copying via a small buffer for testing
	bufSize := 10

	var input = bytes.NewBuffer(nil)
	var output = bytes.NewBuffer(nil)

	err := WriteMessage(input, []byte("0123456789012"))
	if err != nil {
		t.Errorf("WriteMessage 1: %v", err)
	}
	err = WriteMessage(input, []byte("1123456789012"))
	if err != nil {
		t.Errorf("WriteMessage 2: %v", err)
	}

	var reader io.Reader = input

	if _, isBufioReader := reader.(*bufio.Reader); !isBufioReader {
		reader = bufio.NewReaderSize(reader, bufSize)
	}

	// buf := make([]byte, bufSize)
	var counter int64
	err = copyBuffer(output, reader, &counter)
	if err != nil {
		log.Printf("Moved %d bytes: %v\n", counter, err)
	}
	println("copy buffer completed: ", counter)

	time.Sleep(100 * time.Millisecond)

	var lineCounter int
	err = ProcessMessage(output, func(b []byte) error {
		lineCounter++
		println("processed message", lineCounter, ":", string(b), ".")
		return nil
	})
	if err != nil {
		t.Errorf("ProcessMessage: %v", err)
	}

	if lineCounter != 2 {
		t.Errorf("line count: %d, expecting %d", lineCounter, 2)
	}

}