main.go

package main

import "regexp"

func main() {

}

func regex(name string) bool {
	ok, _ := regexp.MatchString("^[a-zA-Z0-9_]+$", name)
	return ok
}

func regexreplace(s string) bool {
	for i := 0; i < len(s); i++ {
		if s[i] < 48 || s[i] < 65 && s[i] > 57 || s[i] > 122 {
			return false
		}
	}
	return true
}

main_test.go

package main

import (
	"math/rand"
	"testing"
)

var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_")

func randSeq(n int) string {
	b := make([]rune, n)
	for i := range b {
		b[i] = letters[rand.Intn(len(letters))]
	}
	return string(b)
}

func BenchmarkRegex(b *testing.B) {
	name := randSeq(16)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		regex(name)
	}
}

func BenchmarkLoop(b *testing.B) {
	name := randSeq(16)
	b.ResetTimer()
	regexreplace(name)
	for i := 0; i < b.N; i++ {
		regexreplace(name)
	}
}

var validnames = [...]string{"Notch", "Geb", "Iron_Man1", "asdfghteahlejhgs", "_TestMe_", "l1lyPad00_"}
var invalidnames = [...]string{"(*$&", "The-King68", " hell0", "symb@l"}

func TestRegex(t *testing.T) {
	for i := 0; i < len(validnames); i++ {
		result := regex(validnames[i])
		if !result {
			t.Fail()
		}
	}

	for i := 0; i < len(invalidnames); i++ {
		result := regex(invalidnames[i])
		if result {
			t.Fail()
		}
	}
}

func TestReplace(t *testing.T) {
	for i := 0; i < len(validnames); i++ {
		result := regexreplace(validnames[i])
		if !result {
			t.Fail()
		}
	}

	for i := 0; i < len(invalidnames); i++ {
		result := regexreplace(invalidnames[i])
		if result {
			t.Fail()
		}
	}
}