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: mmap_test.go
    path of file: ./repos/rclone/lib/mmap
    
    the code of the file until where you have to start completion: package mmap

import (
	"fmt"
	"testing"

	"github.com/stretchr/testify/assert"
)

// Constants to control the benchmarking
const (
	maxAllocs = 16 * 1024
)

func TestAllocFree(t *testing.T) {
	const Size = 4096

	b := MustAlloc(Size)
	assert.Equal(t, Size, len(b))

	// check we can write to all the memory
	for i := range b {

    
func BenchmarkAllocFreeForLotsOfAllocations(b *testing.B) {
	const size = 4096
	alloc := func(n int) (allocs [][]byte) {
		for i := 0; i < n; i++ {
			mem := MustAlloc(size)
			mem[0] ^= 0xFF
			allocs = append(allocs, mem)
		}
		return allocs
	}
	free := func(allocs [][]byte) {
		for _, mem := range allocs {
			MustFree(mem)
		}
	}
	for preAllocs := 1; preAllocs <= maxAllocs; preAllocs *= 2 {
		b.Run(fmt.Sprintf("%d", preAllocs), func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				allocs := alloc(preAllocs)
				free(allocs)
			}
		})
	}
}