Require target lra in gcc.dg/pr108095.c

[official-gcc.git] / libgo / go / strings / strings_test.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package strings_test

import (
        "bytes"
        "fmt"
        "io"
        "math/rand"
        "reflect"
        "runtime"
        "strconv"
        . "strings"
        "testing"
        "unicode"
        "unicode/utf8"
        "unsafe"
)

func eq(a, b []string) bool {
        if len(a) != len(b) {
                return false
        }
        for i := 0; i < len(a); i++ {
                if a[i] != b[i] {
                        return false
                }
        }
        return true
}

var abcd = "abcd"
var faces = "☺☻☹"
var commas = "1,2,3,4"
var dots = "1....2....3....4"

type IndexTest struct {
        s   string
        sep string
        out int
}

var indexTests = []IndexTest{
        {"", "", 0},
        {"", "a", -1},
        {"", "foo", -1},
        {"fo", "foo", -1},
        {"foo", "foo", 0},
        {"oofofoofooo", "f", 2},
        {"oofofoofooo", "foo", 4},
        {"barfoobarfoo", "foo", 3},
        {"foo", "", 0},
        {"foo", "o", 1},
        {"abcABCabc", "A", 3},
        // cases with one byte strings - test special case in Index()
        {"", "a", -1},
        {"x", "a", -1},
        {"x", "x", 0},
        {"abc", "a", 0},
        {"abc", "b", 1},
        {"abc", "c", 2},
        {"abc", "x", -1},
        // test special cases in Index() for short strings
        {"", "ab", -1},
        {"bc", "ab", -1},
        {"ab", "ab", 0},
        {"xab", "ab", 1},
        {"xab"[:2], "ab", -1},
        {"", "abc", -1},
        {"xbc", "abc", -1},
        {"abc", "abc", 0},
        {"xabc", "abc", 1},
        {"xabc"[:3], "abc", -1},
        {"xabxc", "abc", -1},
        {"", "abcd", -1},
        {"xbcd", "abcd", -1},
        {"abcd", "abcd", 0},
        {"xabcd", "abcd", 1},
        {"xyabcd"[:5], "abcd", -1},
        {"xbcqq", "abcqq", -1},
        {"abcqq", "abcqq", 0},
        {"xabcqq", "abcqq", 1},
        {"xyabcqq"[:6], "abcqq", -1},
        {"xabxcqq", "abcqq", -1},
        {"xabcqxq", "abcqq", -1},
        {"", "01234567", -1},
        {"32145678", "01234567", -1},
        {"01234567", "01234567", 0},
        {"x01234567", "01234567", 1},
        {"x0123456x01234567", "01234567", 9},
        {"xx01234567"[:9], "01234567", -1},
        {"", "0123456789", -1},
        {"3214567844", "0123456789", -1},
        {"0123456789", "0123456789", 0},
        {"x0123456789", "0123456789", 1},
        {"x012345678x0123456789", "0123456789", 11},
        {"xyz0123456789"[:12], "0123456789", -1},
        {"x01234567x89", "0123456789", -1},
        {"", "0123456789012345", -1},
        {"3214567889012345", "0123456789012345", -1},
        {"0123456789012345", "0123456789012345", 0},
        {"x0123456789012345", "0123456789012345", 1},
        {"x012345678901234x0123456789012345", "0123456789012345", 17},
        {"", "01234567890123456789", -1},
        {"32145678890123456789", "01234567890123456789", -1},
        {"01234567890123456789", "01234567890123456789", 0},
        {"x01234567890123456789", "01234567890123456789", 1},
        {"x0123456789012345678x01234567890123456789", "01234567890123456789", 21},
        {"xyz01234567890123456789"[:22], "01234567890123456789", -1},
        {"", "0123456789012345678901234567890", -1},
        {"321456788901234567890123456789012345678911", "0123456789012345678901234567890", -1},
        {"0123456789012345678901234567890", "0123456789012345678901234567890", 0},
        {"x0123456789012345678901234567890", "0123456789012345678901234567890", 1},
        {"x012345678901234567890123456789x0123456789012345678901234567890", "0123456789012345678901234567890", 32},
        {"xyz0123456789012345678901234567890"[:33], "0123456789012345678901234567890", -1},
        {"", "01234567890123456789012345678901", -1},
        {"32145678890123456789012345678901234567890211", "01234567890123456789012345678901", -1},
        {"01234567890123456789012345678901", "01234567890123456789012345678901", 0},
        {"x01234567890123456789012345678901", "01234567890123456789012345678901", 1},
        {"x0123456789012345678901234567890x01234567890123456789012345678901", "01234567890123456789012345678901", 33},
        {"xyz01234567890123456789012345678901"[:34], "01234567890123456789012345678901", -1},
        {"xxxxxx012345678901234567890123456789012345678901234567890123456789012", "012345678901234567890123456789012345678901234567890123456789012", 6},
        {"", "0123456789012345678901234567890123456789", -1},
        {"xx012345678901234567890123456789012345678901234567890123456789012", "0123456789012345678901234567890123456789", 2},
        {"xx012345678901234567890123456789012345678901234567890123456789012"[:41], "0123456789012345678901234567890123456789", -1},
        {"xx012345678901234567890123456789012345678901234567890123456789012", "0123456789012345678901234567890123456xxx", -1},
        {"xx0123456789012345678901234567890123456789012345678901234567890120123456789012345678901234567890123456xxx", "0123456789012345678901234567890123456xxx", 65},
        // test fallback to Rabin-Karp.
        {"oxoxoxoxoxoxoxoxoxoxoxoy", "oy", 22},
        {"oxoxoxoxoxoxoxoxoxoxoxox", "oy", -1},
}

var lastIndexTests = []IndexTest{
        {"", "", 0},
        {"", "a", -1},
        {"", "foo", -1},
        {"fo", "foo", -1},
        {"foo", "foo", 0},
        {"foo", "f", 0},
        {"oofofoofooo", "f", 7},
        {"oofofoofooo", "foo", 7},
        {"barfoobarfoo", "foo", 9},
        {"foo", "", 3},
        {"foo", "o", 2},
        {"abcABCabc", "A", 3},
        {"abcABCabc", "a", 6},
}

var indexAnyTests = []IndexTest{
        {"", "", -1},
        {"", "a", -1},
        {"", "abc", -1},
        {"a", "", -1},
        {"a", "a", 0},
        {"\x80", "\xffb", 0},
        {"aaa", "a", 0},
        {"abc", "xyz", -1},
        {"abc", "xcz", 2},
        {"ab☺c", "x☺yz", 2},
        {"a☺b☻c☹d", "cx", len("a☺b☻")},
        {"a☺b☻c☹d", "uvw☻xyz", len("a☺b")},
        {"aRegExp*", ".(|)*+?^$[]", 7},
        {dots + dots + dots, " ", -1},
        {"012abcba210", "\xffb", 4},
        {"012\x80bcb\x80210", "\xffb", 3},
        {"0123456\xcf\x80abc", "\xcfb\x80", 10},
}

var lastIndexAnyTests = []IndexTest{
        {"", "", -1},
        {"", "a", -1},
        {"", "abc", -1},
        {"a", "", -1},
        {"a", "a", 0},
        {"\x80", "\xffb", 0},
        {"aaa", "a", 2},
        {"abc", "xyz", -1},
        {"abc", "ab", 1},
        {"ab☺c", "x☺yz", 2},
        {"a☺b☻c☹d", "cx", len("a☺b☻")},
        {"a☺b☻c☹d", "uvw☻xyz", len("a☺b")},
        {"a.RegExp*", ".(|)*+?^$[]", 8},
        {dots + dots + dots, " ", -1},
        {"012abcba210", "\xffb", 6},
        {"012\x80bcb\x80210", "\xffb", 7},
        {"0123456\xcf\x80abc", "\xcfb\x80", 10},
}

// Execute f on each test case.  funcName should be the name of f; it's used
// in failure reports.
func runIndexTests(t *testing.T, f func(s, sep string) int, funcName string, testCases []IndexTest) {
        for _, test := range testCases {
                actual := f(test.s, test.sep)
                if actual != test.out {
                        t.Errorf("%s(%q,%q) = %v; want %v", funcName, test.s, test.sep, actual, test.out)
                }
        }
}

func TestIndex(t *testing.T)     { runIndexTests(t, Index, "Index", indexTests) }
func TestLastIndex(t *testing.T) { runIndexTests(t, LastIndex, "LastIndex", lastIndexTests) }
func TestIndexAny(t *testing.T)  { runIndexTests(t, IndexAny, "IndexAny", indexAnyTests) }
func TestLastIndexAny(t *testing.T) {
        runIndexTests(t, LastIndexAny, "LastIndexAny", lastIndexAnyTests)
}

func TestIndexByte(t *testing.T) {
        for _, tt := range indexTests {
                if len(tt.sep) != 1 {
                        continue
                }
                pos := IndexByte(tt.s, tt.sep[0])
                if pos != tt.out {
                        t.Errorf(`IndexByte(%q, %q) = %v; want %v`, tt.s, tt.sep[0], pos, tt.out)
                }
        }
}

func TestLastIndexByte(t *testing.T) {
        testCases := []IndexTest{
                {"", "q", -1},
                {"abcdef", "q", -1},
                {"abcdefabcdef", "a", len("abcdef")},      // something in the middle
                {"abcdefabcdef", "f", len("abcdefabcde")}, // last byte
                {"zabcdefabcdef", "z", 0},                 // first byte
                {"a☺b☻c☹d", "b", len("a☺")},               // non-ascii
        }
        for _, test := range testCases {
                actual := LastIndexByte(test.s, test.sep[0])
                if actual != test.out {
                        t.Errorf("LastIndexByte(%q,%c) = %v; want %v", test.s, test.sep[0], actual, test.out)
                }
        }
}

func simpleIndex(s, sep string) int {
        n := len(sep)
        for i := n; i <= len(s); i++ {
                if s[i-n:i] == sep {
                        return i - n
                }
        }
        return -1
}

func TestIndexRandom(t *testing.T) {
        const chars = "abcdefghijklmnopqrstuvwxyz0123456789"
        for times := 0; times < 10; times++ {
                for strLen := 5 + rand.Intn(5); strLen < 140; strLen += 10 { // Arbitrary
                        s1 := make([]byte, strLen)
                        for i := range s1 {
                                s1[i] = chars[rand.Intn(len(chars))]
                        }
                        s := string(s1)
                        for i := 0; i < 50; i++ {
                                begin := rand.Intn(len(s) + 1)
                                end := begin + rand.Intn(len(s)+1-begin)
                                sep := s[begin:end]
                                if i%4 == 0 {
                                        pos := rand.Intn(len(sep) + 1)
                                        sep = sep[:pos] + "A" + sep[pos:]
                                }
                                want := simpleIndex(s, sep)
                                res := Index(s, sep)
                                if res != want {
                                        t.Errorf("Index(%s,%s) = %d; want %d", s, sep, res, want)
                                }
                        }
                }
        }
}

func TestIndexRune(t *testing.T) {
        tests := []struct {
                in   string
                rune rune
                want int
        }{
                {"", 'a', -1},
                {"", '☺', -1},
                {"foo", '☹', -1},
                {"foo", 'o', 1},
                {"foo☺bar", '☺', 3},
                {"foo☺☻☹bar", '☹', 9},
                {"a A x", 'A', 2},
                {"some_text=some_value", '=', 9},
                {"☺a", 'a', 3},
                {"a☻☺b", '☺', 4},

                // RuneError should match any invalid UTF-8 byte sequence.
                {"�", '�', 0},
                {"\xff", '�', 0},
                {"☻x�", '�', len("☻x")},
                {"☻x\xe2\x98", '�', len("☻x")},
                {"☻x\xe2\x98�", '�', len("☻x")},
                {"☻x\xe2\x98x", '�', len("☻x")},

                // Invalid rune values should never match.
                {"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", -1, -1},
                {"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", 0xD800, -1}, // Surrogate pair
                {"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", utf8.MaxRune + 1, -1},
        }
        for _, tt := range tests {
                if got := IndexRune(tt.in, tt.rune); got != tt.want {
                        t.Errorf("IndexRune(%q, %d) = %v; want %v", tt.in, tt.rune, got, tt.want)
                }
        }

        haystack := "test世界"
        allocs := testing.AllocsPerRun(1000, func() {
                if i := IndexRune(haystack, 's'); i != 2 {
                        t.Fatalf("'s' at %d; want 2", i)
                }
                if i := IndexRune(haystack, '世'); i != 4 {
                        t.Fatalf("'世' at %d; want 4", i)
                }
        })
        if runtime.Compiler == "gccgo" {
                t.Skip("skipping allocations test for gccgo until escape analysis is enabled")
        }
        if allocs != 0 && testing.CoverMode() == "" {
                t.Errorf("expected no allocations, got %f", allocs)
        }
}

const benchmarkString = "some_text=some☺value"

func BenchmarkIndexRune(b *testing.B) {
        if got := IndexRune(benchmarkString, '☺'); got != 14 {
                b.Fatalf("wrong index: expected 14, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                IndexRune(benchmarkString, '☺')
        }
}

var benchmarkLongString = Repeat(" ", 100) + benchmarkString

func BenchmarkIndexRuneLongString(b *testing.B) {
        if got := IndexRune(benchmarkLongString, '☺'); got != 114 {
                b.Fatalf("wrong index: expected 114, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                IndexRune(benchmarkLongString, '☺')
        }
}

func BenchmarkIndexRuneFastPath(b *testing.B) {
        if got := IndexRune(benchmarkString, 'v'); got != 17 {
                b.Fatalf("wrong index: expected 17, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                IndexRune(benchmarkString, 'v')
        }
}

func BenchmarkIndex(b *testing.B) {
        if got := Index(benchmarkString, "v"); got != 17 {
                b.Fatalf("wrong index: expected 17, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                Index(benchmarkString, "v")
        }
}

func BenchmarkLastIndex(b *testing.B) {
        if got := Index(benchmarkString, "v"); got != 17 {
                b.Fatalf("wrong index: expected 17, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                LastIndex(benchmarkString, "v")
        }
}

func BenchmarkIndexByte(b *testing.B) {
        if got := IndexByte(benchmarkString, 'v'); got != 17 {
                b.Fatalf("wrong index: expected 17, got=%d", got)
        }
        for i := 0; i < b.N; i++ {
                IndexByte(benchmarkString, 'v')
        }
}

type SplitTest struct {
        s   string
        sep string
        n   int
        a   []string
}

var splittests = []SplitTest{
        {"", "", -1, []string{}},
        {abcd, "", 2, []string{"a", "bcd"}},
        {abcd, "", 4, []string{"a", "b", "c", "d"}},
        {abcd, "", -1, []string{"a", "b", "c", "d"}},
        {faces, "", -1, []string{"☺", "☻", "☹"}},
        {faces, "", 3, []string{"☺", "☻", "☹"}},
        {faces, "", 17, []string{"☺", "☻", "☹"}},
        {"☺�☹", "", -1, []string{"☺", "�", "☹"}},
        {abcd, "a", 0, nil},
        {abcd, "a", -1, []string{"", "bcd"}},
        {abcd, "z", -1, []string{"abcd"}},
        {commas, ",", -1, []string{"1", "2", "3", "4"}},
        {dots, "...", -1, []string{"1", ".2", ".3", ".4"}},
        {faces, "☹", -1, []string{"☺☻", ""}},
        {faces, "~", -1, []string{faces}},
        {"1 2 3 4", " ", 3, []string{"1", "2", "3 4"}},
        {"1 2", " ", 3, []string{"1", "2"}},
}

func TestSplit(t *testing.T) {
        for _, tt := range splittests {
                a := SplitN(tt.s, tt.sep, tt.n)
                if !eq(a, tt.a) {
                        t.Errorf("Split(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, a, tt.a)
                        continue
                }
                if tt.n == 0 {
                        continue
                }
                s := Join(a, tt.sep)
                if s != tt.s {
                        t.Errorf("Join(Split(%q, %q, %d), %q) = %q", tt.s, tt.sep, tt.n, tt.sep, s)
                }
                if tt.n < 0 {
                        b := Split(tt.s, tt.sep)
                        if !reflect.DeepEqual(a, b) {
                                t.Errorf("Split disagrees with SplitN(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, b, a)
                        }
                }
        }
}

var splitaftertests = []SplitTest{
        {abcd, "a", -1, []string{"a", "bcd"}},
        {abcd, "z", -1, []string{"abcd"}},
        {abcd, "", -1, []string{"a", "b", "c", "d"}},
        {commas, ",", -1, []string{"1,", "2,", "3,", "4"}},
        {dots, "...", -1, []string{"1...", ".2...", ".3...", ".4"}},
        {faces, "☹", -1, []string{"☺☻☹", ""}},
        {faces, "~", -1, []string{faces}},
        {faces, "", -1, []string{"☺", "☻", "☹"}},
        {"1 2 3 4", " ", 3, []string{"1 ", "2 ", "3 4"}},
        {"1 2 3", " ", 3, []string{"1 ", "2 ", "3"}},
        {"1 2", " ", 3, []string{"1 ", "2"}},
        {"123", "", 2, []string{"1", "23"}},
        {"123", "", 17, []string{"1", "2", "3"}},
}

func TestSplitAfter(t *testing.T) {
        for _, tt := range splitaftertests {
                a := SplitAfterN(tt.s, tt.sep, tt.n)
                if !eq(a, tt.a) {
                        t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, a, tt.a)
                        continue
                }
                s := Join(a, "")
                if s != tt.s {
                        t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
                }
                if tt.n < 0 {
                        b := SplitAfter(tt.s, tt.sep)
                        if !reflect.DeepEqual(a, b) {
                                t.Errorf("SplitAfter disagrees with SplitAfterN(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, b, a)
                        }
                }
        }
}

type FieldsTest struct {
        s string
        a []string
}

var fieldstests = []FieldsTest{
        {"", []string{}},
        {" ", []string{}},
        {" \t ", []string{}},
        {"\u2000", []string{}},
        {"  abc  ", []string{"abc"}},
        {"1 2 3 4", []string{"1", "2", "3", "4"}},
        {"1  2  3  4", []string{"1", "2", "3", "4"}},
        {"1\t\t2\t\t3\t4", []string{"1", "2", "3", "4"}},
        {"1\u20002\u20013\u20024", []string{"1", "2", "3", "4"}},
        {"\u2000\u2001\u2002", []string{}},
        {"\n™\t™\n", []string{"™", "™"}},
        {"\n\u20001™2\u2000 \u2001 ™", []string{"1™2", "™"}},
        {"\n1\uFFFD \uFFFD2\u20003\uFFFD4", []string{"1\uFFFD", "\uFFFD2", "3\uFFFD4"}},
        {"1\xFF\u2000\xFF2\xFF \xFF", []string{"1\xFF", "\xFF2\xFF", "\xFF"}},
        {faces, []string{faces}},
}

func TestFields(t *testing.T) {
        for _, tt := range fieldstests {
                a := Fields(tt.s)
                if !eq(a, tt.a) {
                        t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
                        continue
                }
        }
}

var FieldsFuncTests = []FieldsTest{
        {"", []string{}},
        {"XX", []string{}},
        {"XXhiXXX", []string{"hi"}},
        {"aXXbXXXcX", []string{"a", "b", "c"}},
}

func TestFieldsFunc(t *testing.T) {
        for _, tt := range fieldstests {
                a := FieldsFunc(tt.s, unicode.IsSpace)
                if !eq(a, tt.a) {
                        t.Errorf("FieldsFunc(%q, unicode.IsSpace) = %v; want %v", tt.s, a, tt.a)
                        continue
                }
        }
        pred := func(c rune) bool { return c == 'X' }
        for _, tt := range FieldsFuncTests {
                a := FieldsFunc(tt.s, pred)
                if !eq(a, tt.a) {
                        t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
                }
        }
}

// Test case for any function which accepts and returns a single string.
type StringTest struct {
        in, out string
}

// Execute f on each test case.  funcName should be the name of f; it's used
// in failure reports.
func runStringTests(t *testing.T, f func(string) string, funcName string, testCases []StringTest) {
        for _, tc := range testCases {
                actual := f(tc.in)
                if actual != tc.out {
                        t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out)
                }
        }
}

var upperTests = []StringTest{
        {"", ""},
        {"ONLYUPPER", "ONLYUPPER"},
        {"abc", "ABC"},
        {"AbC123", "ABC123"},
        {"azAZ09_", "AZAZ09_"},
        {"longStrinGwitHmixofsmaLLandcAps", "LONGSTRINGWITHMIXOFSMALLANDCAPS"},
        {"long\u0250string\u0250with\u0250nonascii\u2C6Fchars", "LONG\u2C6FSTRING\u2C6FWITH\u2C6FNONASCII\u2C6FCHARS"},
        {"\u0250\u0250\u0250\u0250\u0250", "\u2C6F\u2C6F\u2C6F\u2C6F\u2C6F"}, // grows one byte per char
        {"a\u0080\U0010FFFF", "A\u0080\U0010FFFF"},                           // test utf8.RuneSelf and utf8.MaxRune
}

var lowerTests = []StringTest{
        {"", ""},
        {"abc", "abc"},
        {"AbC123", "abc123"},
        {"azAZ09_", "azaz09_"},
        {"longStrinGwitHmixofsmaLLandcAps", "longstringwithmixofsmallandcaps"},
        {"LONG\u2C6FSTRING\u2C6FWITH\u2C6FNONASCII\u2C6FCHARS", "long\u0250string\u0250with\u0250nonascii\u0250chars"},
        {"\u2C6D\u2C6D\u2C6D\u2C6D\u2C6D", "\u0251\u0251\u0251\u0251\u0251"}, // shrinks one byte per char
        {"A\u0080\U0010FFFF", "a\u0080\U0010FFFF"},                           // test utf8.RuneSelf and utf8.MaxRune
}

const space = "\t\v\r\f\n\u0085\u00a0\u2000\u3000"

var trimSpaceTests = []StringTest{
        {"", ""},
        {"abc", "abc"},
        {space + "abc" + space, "abc"},
        {" ", ""},
        {" \t\r\n \t\t\r\r\n\n ", ""},
        {" \t\r\n x\t\t\r\r\n\n ", "x"},
        {" \u2000\t\r\n x\t\t\r\r\ny\n \u3000", "x\t\t\r\r\ny"},
        {"1 \t\r\n2", "1 \t\r\n2"},
        {" x\x80", "x\x80"},
        {" x\xc0", "x\xc0"},
        {"x \xc0\xc0 ", "x \xc0\xc0"},
        {"x \xc0", "x \xc0"},
        {"x \xc0 ", "x \xc0"},
        {"x \xc0\xc0 ", "x \xc0\xc0"},
        {"x ☺\xc0\xc0 ", "x ☺\xc0\xc0"},
        {"x ☺ ", "x ☺"},
}

func tenRunes(ch rune) string {
        r := make([]rune, 10)
        for i := range r {
                r[i] = ch
        }
        return string(r)
}

// User-defined self-inverse mapping function
func rot13(r rune) rune {
        step := rune(13)
        if r >= 'a' && r <= 'z' {
                return ((r - 'a' + step) % 26) + 'a'
        }
        if r >= 'A' && r <= 'Z' {
                return ((r - 'A' + step) % 26) + 'A'
        }
        return r
}

func TestMap(t *testing.T) {
        // Run a couple of awful growth/shrinkage tests
        a := tenRunes('a')
        // 1.  Grow. This triggers two reallocations in Map.
        maxRune := func(rune) rune { return unicode.MaxRune }
        m := Map(maxRune, a)
        expect := tenRunes(unicode.MaxRune)
        if m != expect {
                t.Errorf("growing: expected %q got %q", expect, m)
        }

        // 2. Shrink
        minRune := func(rune) rune { return 'a' }
        m = Map(minRune, tenRunes(unicode.MaxRune))
        expect = a
        if m != expect {
                t.Errorf("shrinking: expected %q got %q", expect, m)
        }

        // 3. Rot13
        m = Map(rot13, "a to zed")
        expect = "n gb mrq"
        if m != expect {
                t.Errorf("rot13: expected %q got %q", expect, m)
        }

        // 4. Rot13^2
        m = Map(rot13, Map(rot13, "a to zed"))
        expect = "a to zed"
        if m != expect {
                t.Errorf("rot13: expected %q got %q", expect, m)
        }

        // 5. Drop
        dropNotLatin := func(r rune) rune {
                if unicode.Is(unicode.Latin, r) {
                        return r
                }
                return -1
        }
        m = Map(dropNotLatin, "Hello, 세계")
        expect = "Hello"
        if m != expect {
                t.Errorf("drop: expected %q got %q", expect, m)
        }

        // 6. Identity
        identity := func(r rune) rune {
                return r
        }
        orig := "Input string that we expect not to be copied."
        m = Map(identity, orig)
        if (*reflect.StringHeader)(unsafe.Pointer(&orig)).Data !=
                (*reflect.StringHeader)(unsafe.Pointer(&m)).Data {
                t.Error("unexpected copy during identity map")
        }

        // 7. Handle invalid UTF-8 sequence
        replaceNotLatin := func(r rune) rune {
                if unicode.Is(unicode.Latin, r) {
                        return r
                }
                return utf8.RuneError
        }
        m = Map(replaceNotLatin, "Hello\255World")
        expect = "Hello\uFFFDWorld"
        if m != expect {
                t.Errorf("replace invalid sequence: expected %q got %q", expect, m)
        }

        // 8. Check utf8.RuneSelf and utf8.MaxRune encoding
        encode := func(r rune) rune {
                switch r {
                case utf8.RuneSelf:
                        return unicode.MaxRune
                case unicode.MaxRune:
                        return utf8.RuneSelf
                }
                return r
        }
        s := string(rune(utf8.RuneSelf)) + string(utf8.MaxRune)
        r := string(utf8.MaxRune) + string(rune(utf8.RuneSelf)) // reverse of s
        m = Map(encode, s)
        if m != r {
                t.Errorf("encoding not handled correctly: expected %q got %q", r, m)
        }
        m = Map(encode, r)
        if m != s {
                t.Errorf("encoding not handled correctly: expected %q got %q", s, m)
        }

        // 9. Check mapping occurs in the front, middle and back
        trimSpaces := func(r rune) rune {
                if unicode.IsSpace(r) {
                        return -1
                }
                return r
        }
        m = Map(trimSpaces, "   abc    123   ")
        expect = "abc123"
        if m != expect {
                t.Errorf("trimSpaces: expected %q got %q", expect, m)
        }
}

func TestToUpper(t *testing.T) { runStringTests(t, ToUpper, "ToUpper", upperTests) }

func TestToLower(t *testing.T) { runStringTests(t, ToLower, "ToLower", lowerTests) }

var toValidUTF8Tests = []struct {
        in   string
        repl string
        out  string
}{
        {"", "\uFFFD", ""},
        {"abc", "\uFFFD", "abc"},
        {"\uFDDD", "\uFFFD", "\uFDDD"},
        {"a\xffb", "\uFFFD", "a\uFFFDb"},
        {"a\xffb\uFFFD", "X", "aXb\uFFFD"},
        {"a☺\xffb☺\xC0\xAFc☺\xff", "", "a☺b☺c☺"},
        {"a☺\xffb☺\xC0\xAFc☺\xff", "日本語", "a☺日本語b☺日本語c☺日本語"},
        {"\xC0\xAF", "\uFFFD", "\uFFFD"},
        {"\xE0\x80\xAF", "\uFFFD", "\uFFFD"},
        {"\xed\xa0\x80", "abc", "abc"},
        {"\xed\xbf\xbf", "\uFFFD", "\uFFFD"},
        {"\xF0\x80\x80\xaf", "☺", "☺"},
        {"\xF8\x80\x80\x80\xAF", "\uFFFD", "\uFFFD"},
        {"\xFC\x80\x80\x80\x80\xAF", "\uFFFD", "\uFFFD"},
}

func TestToValidUTF8(t *testing.T) {
        for _, tc := range toValidUTF8Tests {
                got := ToValidUTF8(tc.in, tc.repl)
                if got != tc.out {
                        t.Errorf("ToValidUTF8(%q, %q) = %q; want %q", tc.in, tc.repl, got, tc.out)
                }
        }
}

func BenchmarkToUpper(b *testing.B) {
        for _, tc := range upperTests {
                b.Run(tc.in, func(b *testing.B) {
                        for i := 0; i < b.N; i++ {
                                actual := ToUpper(tc.in)
                                if actual != tc.out {
                                        b.Errorf("ToUpper(%q) = %q; want %q", tc.in, actual, tc.out)
                                }
                        }
                })
        }
}

func BenchmarkToLower(b *testing.B) {
        for _, tc := range lowerTests {
                b.Run(tc.in, func(b *testing.B) {
                        for i := 0; i < b.N; i++ {
                                actual := ToLower(tc.in)
                                if actual != tc.out {
                                        b.Errorf("ToLower(%q) = %q; want %q", tc.in, actual, tc.out)
                                }
                        }
                })
        }
}

func BenchmarkMapNoChanges(b *testing.B) {
        identity := func(r rune) rune {
                return r
        }
        for i := 0; i < b.N; i++ {
                Map(identity, "Some string that won't be modified.")
        }
}

func TestSpecialCase(t *testing.T) {
        lower := "abcçdefgğhıijklmnoöprsştuüvyz"
        upper := "ABCÇDEFGĞHIİJKLMNOÖPRSŞTUÜVYZ"
        u := ToUpperSpecial(unicode.TurkishCase, upper)
        if u != upper {
                t.Errorf("Upper(upper) is %s not %s", u, upper)
        }
        u = ToUpperSpecial(unicode.TurkishCase, lower)
        if u != upper {
                t.Errorf("Upper(lower) is %s not %s", u, upper)
        }
        l := ToLowerSpecial(unicode.TurkishCase, lower)
        if l != lower {
                t.Errorf("Lower(lower) is %s not %s", l, lower)
        }
        l = ToLowerSpecial(unicode.TurkishCase, upper)
        if l != lower {
                t.Errorf("Lower(upper) is %s not %s", l, lower)
        }
}

func TestTrimSpace(t *testing.T) { runStringTests(t, TrimSpace, "TrimSpace", trimSpaceTests) }

var trimTests = []struct {
        f            string
        in, arg, out string
}{
        {"Trim", "abba", "a", "bb"},
        {"Trim", "abba", "ab", ""},
        {"TrimLeft", "abba", "ab", ""},
        {"TrimRight", "abba", "ab", ""},
        {"TrimLeft", "abba", "a", "bba"},
        {"TrimLeft", "abba", "b", "abba"},
        {"TrimRight", "abba", "a", "abb"},
        {"TrimRight", "abba", "b", "abba"},
        {"Trim", "<tag>", "<>", "tag"},
        {"Trim", "* listitem", " *", "listitem"},
        {"Trim", `"quote"`, `"`, "quote"},
        {"Trim", "\u2C6F\u2C6F\u0250\u0250\u2C6F\u2C6F", "\u2C6F", "\u0250\u0250"},
        {"Trim", "\x80test\xff", "\xff", "test"},
        {"Trim", " Ġ ", " ", "Ġ"},
        {"Trim", " Ġİ0", "0 ", "Ġİ"},
        //empty string tests
        {"Trim", "abba", "", "abba"},
        {"Trim", "", "123", ""},
        {"Trim", "", "", ""},
        {"TrimLeft", "abba", "", "abba"},
        {"TrimLeft", "", "123", ""},
        {"TrimLeft", "", "", ""},
        {"TrimRight", "abba", "", "abba"},
        {"TrimRight", "", "123", ""},
        {"TrimRight", "", "", ""},
        {"TrimRight", "☺\xc0", "☺", "☺\xc0"},
        {"TrimPrefix", "aabb", "a", "abb"},
        {"TrimPrefix", "aabb", "b", "aabb"},
        {"TrimSuffix", "aabb", "a", "aabb"},
        {"TrimSuffix", "aabb", "b", "aab"},
}

func TestTrim(t *testing.T) {
        for _, tc := range trimTests {
                name := tc.f
                var f func(string, string) string
                switch name {
                case "Trim":
                        f = Trim
                case "TrimLeft":
                        f = TrimLeft
                case "TrimRight":
                        f = TrimRight
                case "TrimPrefix":
                        f = TrimPrefix
                case "TrimSuffix":
                        f = TrimSuffix
                default:
                        t.Errorf("Undefined trim function %s", name)
                }
                actual := f(tc.in, tc.arg)
                if actual != tc.out {
                        t.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
                }
        }
}

func BenchmarkTrim(b *testing.B) {
        b.ReportAllocs()

        for i := 0; i < b.N; i++ {
                for _, tc := range trimTests {
                        name := tc.f
                        var f func(string, string) string
                        switch name {
                        case "Trim":
                                f = Trim
                        case "TrimLeft":
                                f = TrimLeft
                        case "TrimRight":
                                f = TrimRight
                        case "TrimPrefix":
                                f = TrimPrefix
                        case "TrimSuffix":
                                f = TrimSuffix
                        default:
                                b.Errorf("Undefined trim function %s", name)
                        }
                        actual := f(tc.in, tc.arg)
                        if actual != tc.out {
                                b.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
                        }
                }
        }
}

func BenchmarkToValidUTF8(b *testing.B) {
        tests := []struct {
                name  string
                input string
        }{
                {"Valid", "typical"},
                {"InvalidASCII", "foo\xffbar"},
                {"InvalidNonASCII", "日本語\xff日本語"},
        }
        replacement := "\uFFFD"
        b.ResetTimer()
        for _, test := range tests {
                b.Run(test.name, func(b *testing.B) {
                        for i := 0; i < b.N; i++ {
                                ToValidUTF8(test.input, replacement)
                        }
                })
        }
}

type predicate struct {
        f    func(rune) bool
        name string
}

var isSpace = predicate{unicode.IsSpace, "IsSpace"}
var isDigit = predicate{unicode.IsDigit, "IsDigit"}
var isUpper = predicate{unicode.IsUpper, "IsUpper"}
var isValidRune = predicate{
        func(r rune) bool {
                return r != utf8.RuneError
        },
        "IsValidRune",
}

func not(p predicate) predicate {
        return predicate{
                func(r rune) bool {
                        return !p.f(r)
                },
                "not " + p.name,
        }
}

var trimFuncTests = []struct {
        f        predicate
        in       string
        trimOut  string
        leftOut  string
        rightOut string
}{
        {isSpace, space + " hello " + space,
                "hello",
                "hello " + space,
                space + " hello"},
        {isDigit, "\u0e50\u0e5212hello34\u0e50\u0e51",
                "hello",
                "hello34\u0e50\u0e51",
                "\u0e50\u0e5212hello"},
        {isUpper, "\u2C6F\u2C6F\u2C6F\u2C6FABCDhelloEF\u2C6F\u2C6FGH\u2C6F\u2C6F",
                "hello",
                "helloEF\u2C6F\u2C6FGH\u2C6F\u2C6F",
                "\u2C6F\u2C6F\u2C6F\u2C6FABCDhello"},
        {not(isSpace), "hello" + space + "hello",
                space,
                space + "hello",
                "hello" + space},
        {not(isDigit), "hello\u0e50\u0e521234\u0e50\u0e51helo",
                "\u0e50\u0e521234\u0e50\u0e51",
                "\u0e50\u0e521234\u0e50\u0e51helo",
                "hello\u0e50\u0e521234\u0e50\u0e51"},
        {isValidRune, "ab\xc0a\xc0cd",
                "\xc0a\xc0",
                "\xc0a\xc0cd",
                "ab\xc0a\xc0"},
        {not(isValidRune), "\xc0a\xc0",
                "a",
                "a\xc0",
                "\xc0a"},
        {isSpace, "",
                "",
                "",
                ""},
        {isSpace, " ",
                "",
                "",
                ""},
}

func TestTrimFunc(t *testing.T) {
        for _, tc := range trimFuncTests {
                trimmers := []struct {
                        name string
                        trim func(s string, f func(r rune) bool) string
                        out  string
                }{
                        {"TrimFunc", TrimFunc, tc.trimOut},
                        {"TrimLeftFunc", TrimLeftFunc, tc.leftOut},
                        {"TrimRightFunc", TrimRightFunc, tc.rightOut},
                }
                for _, trimmer := range trimmers {
                        actual := trimmer.trim(tc.in, tc.f.f)
                        if actual != trimmer.out {
                                t.Errorf("%s(%q, %q) = %q; want %q", trimmer.name, tc.in, tc.f.name, actual, trimmer.out)
                        }
                }
        }
}

var indexFuncTests = []struct {
        in          string
        f           predicate
        first, last int
}{
        {"", isValidRune, -1, -1},
        {"abc", isDigit, -1, -1},
        {"0123", isDigit, 0, 3},
        {"a1b", isDigit, 1, 1},
        {space, isSpace, 0, len(space) - 3}, // last rune in space is 3 bytes
        {"\u0e50\u0e5212hello34\u0e50\u0e51", isDigit, 0, 18},
        {"\u2C6F\u2C6F\u2C6F\u2C6FABCDhelloEF\u2C6F\u2C6FGH\u2C6F\u2C6F", isUpper, 0, 34},
        {"12\u0e50\u0e52hello34\u0e50\u0e51", not(isDigit), 8, 12},

        // tests of invalid UTF-8
        {"\x801", isDigit, 1, 1},
        {"\x80abc", isDigit, -1, -1},
        {"\xc0a\xc0", isValidRune, 1, 1},
        {"\xc0a\xc0", not(isValidRune), 0, 2},
        {"\xc0☺\xc0", not(isValidRune), 0, 4},
        {"\xc0☺\xc0\xc0", not(isValidRune), 0, 5},
        {"ab\xc0a\xc0cd", not(isValidRune), 2, 4},
        {"a\xe0\x80cd", not(isValidRune), 1, 2},
        {"\x80\x80\x80\x80", not(isValidRune), 0, 3},
}

func TestIndexFunc(t *testing.T) {
        for _, tc := range indexFuncTests {
                first := IndexFunc(tc.in, tc.f.f)
                if first != tc.first {
                        t.Errorf("IndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, first, tc.first)
                }
                last := LastIndexFunc(tc.in, tc.f.f)
                if last != tc.last {
                        t.Errorf("LastIndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, last, tc.last)
                }
        }
}

func equal(m string, s1, s2 string, t *testing.T) bool {
        if s1 == s2 {
                return true
        }
        e1 := Split(s1, "")
        e2 := Split(s2, "")
        for i, c1 := range e1 {
                if i >= len(e2) {
                        break
                }
                r1, _ := utf8.DecodeRuneInString(c1)
                r2, _ := utf8.DecodeRuneInString(e2[i])
                if r1 != r2 {
                        t.Errorf("%s diff at %d: U+%04X U+%04X", m, i, r1, r2)
                }
        }
        return false
}

func TestCaseConsistency(t *testing.T) {
        // Make a string of all the runes.
        numRunes := int(unicode.MaxRune + 1)
        if testing.Short() {
                numRunes = 1000
        }
        a := make([]rune, numRunes)
        for i := range a {
                a[i] = rune(i)
        }
        s := string(a)
        // convert the cases.
        upper := ToUpper(s)
        lower := ToLower(s)

        // Consistency checks
        if n := utf8.RuneCountInString(upper); n != numRunes {
                t.Error("rune count wrong in upper:", n)
        }
        if n := utf8.RuneCountInString(lower); n != numRunes {
                t.Error("rune count wrong in lower:", n)
        }
        if !equal("ToUpper(upper)", ToUpper(upper), upper, t) {
                t.Error("ToUpper(upper) consistency fail")
        }
        if !equal("ToLower(lower)", ToLower(lower), lower, t) {
                t.Error("ToLower(lower) consistency fail")
        }
        /*
                  These fail because of non-one-to-oneness of the data, such as multiple
                  upper case 'I' mapping to 'i'.  We comment them out but keep them for
                  interest.
                  For instance: CAPITAL LETTER I WITH DOT ABOVE:
                        unicode.ToUpper(unicode.ToLower('\u0130')) != '\u0130'

                if !equal("ToUpper(lower)", ToUpper(lower), upper, t) {
                        t.Error("ToUpper(lower) consistency fail");
                }
                if !equal("ToLower(upper)", ToLower(upper), lower, t) {
                        t.Error("ToLower(upper) consistency fail");
                }
        */
}

var RepeatTests = []struct {
        in, out string
        count   int
}{
        {"", "", 0},
        {"", "", 1},
        {"", "", 2},
        {"-", "", 0},
        {"-", "-", 1},
        {"-", "----------", 10},
        {"abc ", "abc abc abc ", 3},
}

func TestRepeat(t *testing.T) {
        for _, tt := range RepeatTests {
                a := Repeat(tt.in, tt.count)
                if !equal("Repeat(s)", a, tt.out, t) {
                        t.Errorf("Repeat(%v, %d) = %v; want %v", tt.in, tt.count, a, tt.out)
                        continue
                }
        }
}

func repeat(s string, count int) (err error) {
        defer func() {
                if r := recover(); r != nil {
                        switch v := r.(type) {
                        case error:
                                err = v
                        default:
                                err = fmt.Errorf("%s", v)
                        }
                }
        }()

        Repeat(s, count)

        return
}

// See Issue golang.org/issue/16237
func TestRepeatCatchesOverflow(t *testing.T) {
        tests := [...]struct {
                s      string
                count  int
                errStr string
        }{
                0: {"--", -2147483647, "negative"},
                1: {"", int(^uint(0) >> 1), ""},
                2: {"-", 10, ""},
                3: {"gopher", 0, ""},
                4: {"-", -1, "negative"},
                5: {"--", -102, "negative"},
                6: {string(make([]byte, 255)), int((^uint(0))/255 + 1), "overflow"},
        }

        for i, tt := range tests {
                err := repeat(tt.s, tt.count)
                if tt.errStr == "" {
                        if err != nil {
                                t.Errorf("#%d panicked %v", i, err)
                        }
                        continue
                }

                if err == nil || !Contains(err.Error(), tt.errStr) {
                        t.Errorf("#%d expected %q got %q", i, tt.errStr, err)
                }
        }
}

func runesEqual(a, b []rune) bool {
        if len(a) != len(b) {
                return false
        }
        for i, r := range a {
                if r != b[i] {
                        return false
                }
        }
        return true
}

var RunesTests = []struct {
        in    string
        out   []rune
        lossy bool
}{
        {"", []rune{}, false},
        {" ", []rune{32}, false},
        {"ABC", []rune{65, 66, 67}, false},
        {"abc", []rune{97, 98, 99}, false},
        {"\u65e5\u672c\u8a9e", []rune{26085, 26412, 35486}, false},
        {"ab\x80c", []rune{97, 98, 0xFFFD, 99}, true},
        {"ab\xc0c", []rune{97, 98, 0xFFFD, 99}, true},
}

func TestRunes(t *testing.T) {
        for _, tt := range RunesTests {
                a := []rune(tt.in)
                if !runesEqual(a, tt.out) {
                        t.Errorf("[]rune(%q) = %v; want %v", tt.in, a, tt.out)
                        continue
                }
                if !tt.lossy {
                        // can only test reassembly if we didn't lose information
                        s := string(a)
                        if s != tt.in {
                                t.Errorf("string([]rune(%q)) = %x; want %x", tt.in, s, tt.in)
                        }
                }
        }
}

func TestReadByte(t *testing.T) {
        testStrings := []string{"", abcd, faces, commas}
        for _, s := range testStrings {
                reader := NewReader(s)
                if e := reader.UnreadByte(); e == nil {
                        t.Errorf("Unreading %q at beginning: expected error", s)
                }
                var res bytes.Buffer
                for {
                        b, e := reader.ReadByte()
                        if e == io.EOF {
                                break
                        }
                        if e != nil {
                                t.Errorf("Reading %q: %s", s, e)
                                break
                        }
                        res.WriteByte(b)
                        // unread and read again
                        e = reader.UnreadByte()
                        if e != nil {
                                t.Errorf("Unreading %q: %s", s, e)
                                break
                        }
                        b1, e := reader.ReadByte()
                        if e != nil {
                                t.Errorf("Reading %q after unreading: %s", s, e)
                                break
                        }
                        if b1 != b {
                                t.Errorf("Reading %q after unreading: want byte %q, got %q", s, b, b1)
                                break
                        }
                }
                if res.String() != s {
                        t.Errorf("Reader(%q).ReadByte() produced %q", s, res.String())
                }
        }
}

func TestReadRune(t *testing.T) {
        testStrings := []string{"", abcd, faces, commas}
        for _, s := range testStrings {
                reader := NewReader(s)
                if e := reader.UnreadRune(); e == nil {
                        t.Errorf("Unreading %q at beginning: expected error", s)
                }
                res := ""
                for {
                        r, z, e := reader.ReadRune()
                        if e == io.EOF {
                                break
                        }
                        if e != nil {
                                t.Errorf("Reading %q: %s", s, e)
                                break
                        }
                        res += string(r)
                        // unread and read again
                        e = reader.UnreadRune()
                        if e != nil {
                                t.Errorf("Unreading %q: %s", s, e)
                                break
                        }
                        r1, z1, e := reader.ReadRune()
                        if e != nil {
                                t.Errorf("Reading %q after unreading: %s", s, e)
                                break
                        }
                        if r1 != r {
                                t.Errorf("Reading %q after unreading: want rune %q, got %q", s, r, r1)
                                break
                        }
                        if z1 != z {
                                t.Errorf("Reading %q after unreading: want size %d, got %d", s, z, z1)
                                break
                        }
                }
                if res != s {
                        t.Errorf("Reader(%q).ReadRune() produced %q", s, res)
                }
        }
}

var UnreadRuneErrorTests = []struct {
        name string
        f    func(*Reader)
}{
        {"Read", func(r *Reader) { r.Read([]byte{0}) }},
        {"ReadByte", func(r *Reader) { r.ReadByte() }},
        {"UnreadRune", func(r *Reader) { r.UnreadRune() }},
        {"Seek", func(r *Reader) { r.Seek(0, io.SeekCurrent) }},
        {"WriteTo", func(r *Reader) { r.WriteTo(&bytes.Buffer{}) }},
}

func TestUnreadRuneError(t *testing.T) {
        for _, tt := range UnreadRuneErrorTests {
                reader := NewReader("0123456789")
                if _, _, err := reader.ReadRune(); err != nil {
                        // should not happen
                        t.Fatal(err)
                }
                tt.f(reader)
                err := reader.UnreadRune()
                if err == nil {
                        t.Errorf("Unreading after %s: expected error", tt.name)
                }
        }
}

var ReplaceTests = []struct {
        in       string
        old, new string
        n        int
        out      string
}{
        {"hello", "l", "L", 0, "hello"},
        {"hello", "l", "L", -1, "heLLo"},
        {"hello", "x", "X", -1, "hello"},
        {"", "x", "X", -1, ""},
        {"radar", "r", "<r>", -1, "<r>ada<r>"},
        {"", "", "<>", -1, "<>"},
        {"banana", "a", "<>", -1, "b<>n<>n<>"},
        {"banana", "a", "<>", 1, "b<>nana"},
        {"banana", "a", "<>", 1000, "b<>n<>n<>"},
        {"banana", "an", "<>", -1, "b<><>a"},
        {"banana", "ana", "<>", -1, "b<>na"},
        {"banana", "", "<>", -1, "<>b<>a<>n<>a<>n<>a<>"},
        {"banana", "", "<>", 10, "<>b<>a<>n<>a<>n<>a<>"},
        {"banana", "", "<>", 6, "<>b<>a<>n<>a<>n<>a"},
        {"banana", "", "<>", 5, "<>b<>a<>n<>a<>na"},
        {"banana", "", "<>", 1, "<>banana"},
        {"banana", "a", "a", -1, "banana"},
        {"banana", "a", "a", 1, "banana"},
        {"☺☻☹", "", "<>", -1, "<>☺<>☻<>☹<>"},
}

func TestReplace(t *testing.T) {
        for _, tt := range ReplaceTests {
                if s := Replace(tt.in, tt.old, tt.new, tt.n); s != tt.out {
                        t.Errorf("Replace(%q, %q, %q, %d) = %q, want %q", tt.in, tt.old, tt.new, tt.n, s, tt.out)
                }
                if tt.n == -1 {
                        s := ReplaceAll(tt.in, tt.old, tt.new)
                        if s != tt.out {
                                t.Errorf("ReplaceAll(%q, %q, %q) = %q, want %q", tt.in, tt.old, tt.new, s, tt.out)
                        }
                }
        }
}

var TitleTests = []struct {
        in, out string
}{
        {"", ""},
        {"a", "A"},
        {" aaa aaa aaa ", " Aaa Aaa Aaa "},
        {" Aaa Aaa Aaa ", " Aaa Aaa Aaa "},
        {"123a456", "123a456"},
        {"double-blind", "Double-Blind"},
        {"ÿøû", "Ÿøû"},
        {"with_underscore", "With_underscore"},
        {"unicode \xe2\x80\xa8 line separator", "Unicode \xe2\x80\xa8 Line Separator"},
}

func TestTitle(t *testing.T) {
        for _, tt := range TitleTests {
                if s := Title(tt.in); s != tt.out {
                        t.Errorf("Title(%q) = %q, want %q", tt.in, s, tt.out)
                }
        }
}

var ContainsTests = []struct {
        str, substr string
        expected    bool
}{
        {"abc", "bc", true},
        {"abc", "bcd", false},
        {"abc", "", true},
        {"", "a", false},

        // cases to cover code in runtime/asm_amd64.s:indexShortStr
        // 2-byte needle
        {"xxxxxx", "01", false},
        {"01xxxx", "01", true},
        {"xx01xx", "01", true},
        {"xxxx01", "01", true},
        {"01xxxxx"[1:], "01", false},
        {"xxxxx01"[:6], "01", false},
        // 3-byte needle
        {"xxxxxxx", "012", false},
        {"012xxxx", "012", true},
        {"xx012xx", "012", true},
        {"xxxx012", "012", true},
        {"012xxxxx"[1:], "012", false},
        {"xxxxx012"[:7], "012", false},
        // 4-byte needle
        {"xxxxxxxx", "0123", false},
        {"0123xxxx", "0123", true},
        {"xx0123xx", "0123", true},
        {"xxxx0123", "0123", true},
        {"0123xxxxx"[1:], "0123", false},
        {"xxxxx0123"[:8], "0123", false},
        // 5-7-byte needle
        {"xxxxxxxxx", "01234", false},
        {"01234xxxx", "01234", true},
        {"xx01234xx", "01234", true},
        {"xxxx01234", "01234", true},
        {"01234xxxxx"[1:], "01234", false},
        {"xxxxx01234"[:9], "01234", false},
        // 8-byte needle
        {"xxxxxxxxxxxx", "01234567", false},
        {"01234567xxxx", "01234567", true},
        {"xx01234567xx", "01234567", true},
        {"xxxx01234567", "01234567", true},
        {"01234567xxxxx"[1:], "01234567", false},
        {"xxxxx01234567"[:12], "01234567", false},
        // 9-15-byte needle
        {"xxxxxxxxxxxxx", "012345678", false},
        {"012345678xxxx", "012345678", true},
        {"xx012345678xx", "012345678", true},
        {"xxxx012345678", "012345678", true},
        {"012345678xxxxx"[1:], "012345678", false},
        {"xxxxx012345678"[:13], "012345678", false},
        // 16-byte needle
        {"xxxxxxxxxxxxxxxxxxxx", "0123456789ABCDEF", false},
        {"0123456789ABCDEFxxxx", "0123456789ABCDEF", true},
        {"xx0123456789ABCDEFxx", "0123456789ABCDEF", true},
        {"xxxx0123456789ABCDEF", "0123456789ABCDEF", true},
        {"0123456789ABCDEFxxxxx"[1:], "0123456789ABCDEF", false},
        {"xxxxx0123456789ABCDEF"[:20], "0123456789ABCDEF", false},
        // 17-31-byte needle
        {"xxxxxxxxxxxxxxxxxxxxx", "0123456789ABCDEFG", false},
        {"0123456789ABCDEFGxxxx", "0123456789ABCDEFG", true},
        {"xx0123456789ABCDEFGxx", "0123456789ABCDEFG", true},
        {"xxxx0123456789ABCDEFG", "0123456789ABCDEFG", true},
        {"0123456789ABCDEFGxxxxx"[1:], "0123456789ABCDEFG", false},
        {"xxxxx0123456789ABCDEFG"[:21], "0123456789ABCDEFG", false},

        // partial match cases
        {"xx01x", "012", false},                             // 3
        {"xx0123x", "01234", false},                         // 5-7
        {"xx01234567x", "012345678", false},                 // 9-15
        {"xx0123456789ABCDEFx", "0123456789ABCDEFG", false}, // 17-31, issue 15679
}

func TestContains(t *testing.T) {
        for _, ct := range ContainsTests {
                if Contains(ct.str, ct.substr) != ct.expected {
                        t.Errorf("Contains(%s, %s) = %v, want %v",
                                ct.str, ct.substr, !ct.expected, ct.expected)
                }
        }
}

var ContainsAnyTests = []struct {
        str, substr string
        expected    bool
}{
        {"", "", false},
        {"", "a", false},
        {"", "abc", false},
        {"a", "", false},
        {"a", "a", true},
        {"aaa", "a", true},
        {"abc", "xyz", false},
        {"abc", "xcz", true},
        {"a☺b☻c☹d", "uvw☻xyz", true},
        {"aRegExp*", ".(|)*+?^$[]", true},
        {dots + dots + dots, " ", false},
}

func TestContainsAny(t *testing.T) {
        for _, ct := range ContainsAnyTests {
                if ContainsAny(ct.str, ct.substr) != ct.expected {
                        t.Errorf("ContainsAny(%s, %s) = %v, want %v",
                                ct.str, ct.substr, !ct.expected, ct.expected)
                }
        }
}

var ContainsRuneTests = []struct {
        str      string
        r        rune
        expected bool
}{
        {"", 'a', false},
        {"a", 'a', true},
        {"aaa", 'a', true},
        {"abc", 'y', false},
        {"abc", 'c', true},
        {"a☺b☻c☹d", 'x', false},
        {"a☺b☻c☹d", '☻', true},
        {"aRegExp*", '*', true},
}

func TestContainsRune(t *testing.T) {
        for _, ct := range ContainsRuneTests {
                if ContainsRune(ct.str, ct.r) != ct.expected {
                        t.Errorf("ContainsRune(%q, %q) = %v, want %v",
                                ct.str, ct.r, !ct.expected, ct.expected)
                }
        }
}

var EqualFoldTests = []struct {
        s, t string
        out  bool
}{
        {"abc", "abc", true},
        {"ABcd", "ABcd", true},
        {"123abc", "123ABC", true},
        {"αβδ", "ΑΒΔ", true},
        {"abc", "xyz", false},
        {"abc", "XYZ", false},
        {"abcdefghijk", "abcdefghijX", false},
        {"abcdefghijk", "abcdefghij\u212A", true},
        {"abcdefghijK", "abcdefghij\u212A", true},
        {"abcdefghijkz", "abcdefghij\u212Ay", false},
        {"abcdefghijKz", "abcdefghij\u212Ay", false},
        {"1", "2", false},
        {"utf-8", "US-ASCII", false},
}

func TestEqualFold(t *testing.T) {
        for _, tt := range EqualFoldTests {
                if out := EqualFold(tt.s, tt.t); out != tt.out {
                        t.Errorf("EqualFold(%#q, %#q) = %v, want %v", tt.s, tt.t, out, tt.out)
                }
                if out := EqualFold(tt.t, tt.s); out != tt.out {
                        t.Errorf("EqualFold(%#q, %#q) = %v, want %v", tt.t, tt.s, out, tt.out)
                }
        }
}

func BenchmarkEqualFold(b *testing.B) {
        for i := 0; i < b.N; i++ {
                for _, tt := range EqualFoldTests {
                        if out := EqualFold(tt.s, tt.t); out != tt.out {
                                b.Fatal("wrong result")
                        }
                }
        }
}

var CountTests = []struct {
        s, sep string
        num    int
}{
        {"", "", 1},
        {"", "notempty", 0},
        {"notempty", "", 9},
        {"smaller", "not smaller", 0},
        {"12345678987654321", "6", 2},
        {"611161116", "6", 3},
        {"notequal", "NotEqual", 0},
        {"equal", "equal", 1},
        {"abc1231231123q", "123", 3},
        {"11111", "11", 2},
}

func TestCount(t *testing.T) {
        for _, tt := range CountTests {
                if num := Count(tt.s, tt.sep); num != tt.num {
                        t.Errorf("Count(%q, %q) = %d, want %d", tt.s, tt.sep, num, tt.num)
                }
        }
}

var cutTests = []struct {
        s, sep        string
        before, after string
        found         bool
}{
        {"abc", "b", "a", "c", true},
        {"abc", "a", "", "bc", true},
        {"abc", "c", "ab", "", true},
        {"abc", "abc", "", "", true},
        {"abc", "", "", "abc", true},
        {"abc", "d", "abc", "", false},
        {"", "d", "", "", false},
        {"", "", "", "", true},
}

func TestCut(t *testing.T) {
        for _, tt := range cutTests {
                if before, after, found := Cut(tt.s, tt.sep); before != tt.before || after != tt.after || found != tt.found {
                        t.Errorf("Cut(%q, %q) = %q, %q, %v, want %q, %q, %v", tt.s, tt.sep, before, after, found, tt.before, tt.after, tt.found)
                }
        }
}

func makeBenchInputHard() string {
        tokens := [...]string{
                "<a>", "<p>", "<b>", "<strong>",
                "</a>", "</p>", "</b>", "</strong>",
                "hello", "world",
        }
        x := make([]byte, 0, 1<<20)
        for {
                i := rand.Intn(len(tokens))
                if len(x)+len(tokens[i]) >= 1<<20 {
                        break
                }
                x = append(x, tokens[i]...)
        }
        return string(x)
}

var benchInputHard = makeBenchInputHard()

func benchmarkIndexHard(b *testing.B, sep string) {
        for i := 0; i < b.N; i++ {
                Index(benchInputHard, sep)
        }
}

func benchmarkLastIndexHard(b *testing.B, sep string) {
        for i := 0; i < b.N; i++ {
                LastIndex(benchInputHard, sep)
        }
}

func benchmarkCountHard(b *testing.B, sep string) {
        for i := 0; i < b.N; i++ {
                Count(benchInputHard, sep)
        }
}

func BenchmarkIndexHard1(b *testing.B) { benchmarkIndexHard(b, "<>") }
func BenchmarkIndexHard2(b *testing.B) { benchmarkIndexHard(b, "</pre>") }
func BenchmarkIndexHard3(b *testing.B) { benchmarkIndexHard(b, "<b>hello world</b>") }
func BenchmarkIndexHard4(b *testing.B) {
        benchmarkIndexHard(b, "<pre><b>hello</b><strong>world</strong></pre>")
}

func BenchmarkLastIndexHard1(b *testing.B) { benchmarkLastIndexHard(b, "<>") }
func BenchmarkLastIndexHard2(b *testing.B) { benchmarkLastIndexHard(b, "</pre>") }
func BenchmarkLastIndexHard3(b *testing.B) { benchmarkLastIndexHard(b, "<b>hello world</b>") }

func BenchmarkCountHard1(b *testing.B) { benchmarkCountHard(b, "<>") }
func BenchmarkCountHard2(b *testing.B) { benchmarkCountHard(b, "</pre>") }
func BenchmarkCountHard3(b *testing.B) { benchmarkCountHard(b, "<b>hello world</b>") }

var benchInputTorture = Repeat("ABC", 1<<10) + "123" + Repeat("ABC", 1<<10)
var benchNeedleTorture = Repeat("ABC", 1<<10+1)

func BenchmarkIndexTorture(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Index(benchInputTorture, benchNeedleTorture)
        }
}

func BenchmarkCountTorture(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Count(benchInputTorture, benchNeedleTorture)
        }
}

func BenchmarkCountTortureOverlapping(b *testing.B) {
        A := Repeat("ABC", 1<<20)
        B := Repeat("ABC", 1<<10)
        for i := 0; i < b.N; i++ {
                Count(A, B)
        }
}

func BenchmarkCountByte(b *testing.B) {
        indexSizes := []int{10, 32, 4 << 10, 4 << 20, 64 << 20}
        benchStr := Repeat(benchmarkString,
                (indexSizes[len(indexSizes)-1]+len(benchmarkString)-1)/len(benchmarkString))
        benchFunc := func(b *testing.B, benchStr string) {
                b.SetBytes(int64(len(benchStr)))
                for i := 0; i < b.N; i++ {
                        Count(benchStr, "=")
                }
        }
        for _, size := range indexSizes {
                b.Run(fmt.Sprintf("%d", size), func(b *testing.B) {
                        benchFunc(b, benchStr[:size])
                })
        }

}

var makeFieldsInput = func() string {
        x := make([]byte, 1<<20)
        // Input is ~10% space, ~10% 2-byte UTF-8, rest ASCII non-space.
        for i := range x {
                switch rand.Intn(10) {
                case 0:
                        x[i] = ' '
                case 1:
                        if i > 0 && x[i-1] == 'x' {
                                copy(x[i-1:], "χ")
                                break
                        }
                        fallthrough
                default:
                        x[i] = 'x'
                }
        }
        return string(x)
}

var makeFieldsInputASCII = func() string {
        x := make([]byte, 1<<20)
        // Input is ~10% space, rest ASCII non-space.
        for i := range x {
                if rand.Intn(10) == 0 {
                        x[i] = ' '
                } else {
                        x[i] = 'x'
                }
        }
        return string(x)
}

var stringdata = []struct{ name, data string }{
        {"ASCII", makeFieldsInputASCII()},
        {"Mixed", makeFieldsInput()},
}

func BenchmarkFields(b *testing.B) {
        for _, sd := range stringdata {
                b.Run(sd.name, func(b *testing.B) {
                        for j := 1 << 4; j <= 1<<20; j <<= 4 {
                                b.Run(fmt.Sprintf("%d", j), func(b *testing.B) {
                                        b.ReportAllocs()
                                        b.SetBytes(int64(j))
                                        data := sd.data[:j]
                                        for i := 0; i < b.N; i++ {
                                                Fields(data)
                                        }
                                })
                        }
                })
        }
}

func BenchmarkFieldsFunc(b *testing.B) {
        for _, sd := range stringdata {
                b.Run(sd.name, func(b *testing.B) {
                        for j := 1 << 4; j <= 1<<20; j <<= 4 {
                                b.Run(fmt.Sprintf("%d", j), func(b *testing.B) {
                                        b.ReportAllocs()
                                        b.SetBytes(int64(j))
                                        data := sd.data[:j]
                                        for i := 0; i < b.N; i++ {
                                                FieldsFunc(data, unicode.IsSpace)
                                        }
                                })
                        }
                })
        }
}

func BenchmarkSplitEmptySeparator(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Split(benchInputHard, "")
        }
}

func BenchmarkSplitSingleByteSeparator(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Split(benchInputHard, "/")
        }
}

func BenchmarkSplitMultiByteSeparator(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Split(benchInputHard, "hello")
        }
}

func BenchmarkSplitNSingleByteSeparator(b *testing.B) {
        for i := 0; i < b.N; i++ {
                SplitN(benchInputHard, "/", 10)
        }
}

func BenchmarkSplitNMultiByteSeparator(b *testing.B) {
        for i := 0; i < b.N; i++ {
                SplitN(benchInputHard, "hello", 10)
        }
}

func BenchmarkRepeat(b *testing.B) {
        s := "0123456789"
        for _, n := range []int{5, 10} {
                for _, c := range []int{1, 2, 6} {
                        b.Run(fmt.Sprintf("%dx%d", n, c), func(b *testing.B) {
                                for i := 0; i < b.N; i++ {
                                        Repeat(s[:n], c)
                                }
                        })
                }
        }
}

func BenchmarkIndexAnyASCII(b *testing.B) {
        x := Repeat("#", 2048) // Never matches set
        cs := "0123456789abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz"
        for k := 1; k <= 2048; k <<= 4 {
                for j := 1; j <= 64; j <<= 1 {
                        b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
                                for i := 0; i < b.N; i++ {
                                        IndexAny(x[:k], cs[:j])
                                }
                        })
                }
        }
}

func BenchmarkIndexAnyUTF8(b *testing.B) {
        x := Repeat("#", 2048) // Never matches set
        cs := "你好世界, hello world. 你好世界, hello world. 你好世界, hello world."
        for k := 1; k <= 2048; k <<= 4 {
                for j := 1; j <= 64; j <<= 1 {
                        b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
                                for i := 0; i < b.N; i++ {
                                        IndexAny(x[:k], cs[:j])
                                }
                        })
                }
        }
}

func BenchmarkLastIndexAnyASCII(b *testing.B) {
        x := Repeat("#", 2048) // Never matches set
        cs := "0123456789abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz"
        for k := 1; k <= 2048; k <<= 4 {
                for j := 1; j <= 64; j <<= 1 {
                        b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
                                for i := 0; i < b.N; i++ {
                                        LastIndexAny(x[:k], cs[:j])
                                }
                        })
                }
        }
}

func BenchmarkLastIndexAnyUTF8(b *testing.B) {
        x := Repeat("#", 2048) // Never matches set
        cs := "你好世界, hello world. 你好世界, hello world. 你好世界, hello world."
        for k := 1; k <= 2048; k <<= 4 {
                for j := 1; j <= 64; j <<= 1 {
                        b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
                                for i := 0; i < b.N; i++ {
                                        LastIndexAny(x[:k], cs[:j])
                                }
                        })
                }
        }
}

func BenchmarkTrimASCII(b *testing.B) {
        cs := "0123456789abcdef"
        for k := 1; k <= 4096; k <<= 4 {
                for j := 1; j <= 16; j <<= 1 {
                        b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
                                x := Repeat(cs[:j], k) // Always matches set
                                for i := 0; i < b.N; i++ {
                                        Trim(x[:k], cs[:j])
                                }
                        })
                }
        }
}

func BenchmarkTrimByte(b *testing.B) {
        x := "  the quick brown fox   "
        for i := 0; i < b.N; i++ {
                Trim(x, " ")
        }
}

func BenchmarkIndexPeriodic(b *testing.B) {
        key := "aa"
        for _, skip := range [...]int{2, 4, 8, 16, 32, 64} {
                b.Run(fmt.Sprintf("IndexPeriodic%d", skip), func(b *testing.B) {
                        s := Repeat("a"+Repeat(" ", skip-1), 1<<16/skip)
                        for i := 0; i < b.N; i++ {
                                Index(s, key)
                        }
                })
        }
}

func BenchmarkJoin(b *testing.B) {
        vals := []string{"red", "yellow", "pink", "green", "purple", "orange", "blue"}
        for l := 0; l <= len(vals); l++ {
                b.Run(strconv.Itoa(l), func(b *testing.B) {
                        b.ReportAllocs()
                        vals := vals[:l]
                        for i := 0; i < b.N; i++ {
                                Join(vals, " and ")
                        }
                })
        }
}

func BenchmarkTrimSpace(b *testing.B) {
        tests := []struct{ name, input string }{
                {"NoTrim", "typical"},
                {"ASCII", "  foo bar  "},
                {"SomeNonASCII", "    \u2000\t\r\n x\t\t\r\r\ny\n \u3000    "},
                {"JustNonASCII", "\u2000\u2000\u2000☺☺☺☺\u3000\u3000\u3000"},
        }
        for _, test := range tests {
                b.Run(test.name, func(b *testing.B) {
                        for i := 0; i < b.N; i++ {
                                TrimSpace(test.input)
                        }
                })
        }
}

var stringSink string

func BenchmarkReplaceAll(b *testing.B) {
        b.ReportAllocs()
        for i := 0; i < b.N; i++ {
                stringSink = ReplaceAll("banana", "a", "<>")
        }
}