output

$ ./command-line-arguments.test --test.bench="Bench"
testing: warning: no tests to run
PASS
BenchmarkConcat	  200000	     10877 ns/op
BenchmarkJoin	  100000	     16848 ns/op
BenchmarkBuffer	  100000	     20729 ns/op

test.go

package main

import "bytes"
import "strings"
import "testing"


func BenchmarkConcat(b *testing.B) {
	for iter := 0; iter < b.N; iter++ {
                var As = "AAAA"
		var _ = As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+
                        As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+
                        As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+
                        As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+As+
                        As+As+As+As+As+As+As+As
	}
}

func BenchmarkJoin(b *testing.B) {
	for iter := 0; iter < b.N; iter++ {
		sa := make([]string, 100)

		for i := 0; i < 100; i++ {
			sa[i] = "AAAA"
		}

		strings.Join(sa, "")
	}
}

func BenchmarkBuffer(b *testing.B) {
	for iter := 0; iter < b.N; iter++ {
		b := new(bytes.Buffer)
		for i := 0; i < 100; i++ {
			b.WriteString("AAAA")
		}
		b.String()
	}
}