Benchmark for four types of string concatenation

concatbench_test.go

package concatbench

import (
	"fmt"
	"strings"
	"testing"
)

const (
	s1 = "четёре чёрненьких чумазеньких чертёнка, "
	s2 = "чертили чёрными чернилами чертёж, "
)

func BenchmarkPlus(b *testing.B) {
	s := s1
	for i := 0; i < b.N; i++ {
		s = s + s2
	}
	_ = s
}

func BenchmarkSprintf(b *testing.B) {
	s := s1
	for i := 0; i < b.N; i++ {
		s = fmt.Sprintf("%s%s", s, s2)
	}
	_ = s
}

func BenchmarkAppend(b *testing.B) {
	l := []rune(s1)
	for i := 0; i < b.N; i++ {
		l = append(l, []rune(s2)...)
	}
	_ = string(l)
}

func BenchmarkBuilder(b *testing.B) {
	var sb strings.Builder
	sb.WriteString(s1)
	for i := 0; i < b.N; i++ {
		sb.WriteString(s2)
	}
	_ = sb.String()
}

$ go test -benchmem -bench=.
goos: linux
goarch: amd64
BenchmarkPlus-8      	   29947	    129963 ns/op	  947487 B/op	       1 allocs/op
BenchmarkSprintf-8   	   14324	    126644 ns/op	  912833 B/op	       4 allocs/op
BenchmarkAppend-8    	 1995886	       563 ns/op	     873 B/op	       0 allocs/op
BenchmarkBuilder-8   	23572284	        53.2 ns/op	     327 B/op	       0 allocs/op
PASS
ok  	_/home/cpro/work/temp/build	10.010s