Simple Benchmark Test for https://stackoverflow.com/questions/34628476/write-operation-cost

write_test.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strings"
	"testing"
)

var data []string

func TestMain(m *testing.M) {
	os.Exit(initTestSuite(m))
}

func initTestSuite(m *testing.M) int {
	const nRecords int = 100000

	data = make([]string, nRecords)
	record := strings.Repeat("0123456789", 60)

	for i := 0; i < nRecords; i++ {
		data[i] = record
	}

	e := m.Run()
	return e
}

// fut represents the function under test. It will be tested with different given buffer size. If 0 is passed 
// the default buffer size (4K) will be used.
func fut(t *testing.B, bufSize int) {
	f, err := os.Create("file.txt")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()
	w := bufio.NewWriter(f)
	if bufSize > 0 {
		w = bufio.NewWriterSize(w, bufSize)
	}
	//t.Logf("Buffer Size %d", w.Size())
	for _, d := range data {
		_, err := w.WriteString(fmt.Sprint(d + "\n"))
		if err != nil {
			fmt.Println(err)
		}
	}
	err = w.Flush()
	if err != nil {
		log.Fatal(err)
	}
}

func BenchmarkWrite(b *testing.B) {
	tests := []struct {
		name    string
		bufSize int
	}{
		{
			name:    "Default Buffer Size",
			bufSize: 0,
		},
		{
			name:    "Buffer Size 16K",
			bufSize: 16384,
		},
		{
			name:    "Buffer Size 64K",
			bufSize: 65536,
		},
	}

	for _, tc := range tests {
		b.Run(tc.name, func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				fut(b, tc.bufSize)
			}
		})
	}
}