Quickcheck, Reverse, and Runes in Go

reverse_test.go

package main

import (
	"testing"
	"testing/quick"
	"unicode/utf8"
)

func reverseUsingBytes(a string) string {
	b := make([]byte, len(a))
	// a for range loop would have used runes instead of bytes
	for i := 0; i < len(a); i++ {
		b[len(a)-i-1] = a[i]
	}
	return string(b)
}

func reverseUsingRunes(a string) string {
	n := utf8.RuneCountInString(a)
	b := make([]rune, n)
	for i, r := range []rune(a) {
		b[n-i-1] = r
	}
	return string(b)
}

var reverse = reverseUsingRunes

func TestDoubleReverse(t *testing.T) {
	f := func(s string) bool { return reverse(reverse(s)) == s }
	if err := quick.Check(f, nil); err != nil {
		t.Error(err)
	}
}

func TestReverseConcat(t *testing.T) {
	f := func(x, y string) bool {
		return reverse(x)+reverse(y) == reverse(y+x)
	}
	if err := quick.Check(f, nil); err != nil {
		t.Error(err)
	}
}

func TestValidUTF8(t *testing.T) {
	f := func(s string) bool {
		return utf8.ValidString(reverse(s))
	}
	if err := quick.Check(f, nil); err != nil {
		t.Error(err)
	}
}