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Source file src/strings/strings_test.go

Documentation: strings

  // 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"
  	. "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},
  }
  
  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},
  	{"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},
  }
  
  var lastIndexAnyTests = []IndexTest{
  	{"", "", -1},
  	{"", "a", -1},
  	{"", "abc", -1},
  	{"a", "", -1},
  	{"a", "a", 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},
  }
  
  // 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 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 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{
  	{"", ""},
  	{"abc", "ABC"},
  	{"AbC123", "ABC123"},
  	{"azAZ09_", "AZAZ09_"},
  	{"\u0250\u0250\u0250\u0250\u0250", "\u2C6F\u2C6F\u2C6F\u2C6F\u2C6F"}, // grows one byte per char
  }
  
  var lowerTests = []StringTest{
  	{"", ""},
  	{"abc", "abc"},
  	{"AbC123", "abc123"},
  	{"azAZ09_", "azaz09_"},
  	{"\u2C6D\u2C6D\u2C6D\u2C6D\u2C6D", "\u0251\u0251\u0251\u0251\u0251"}, // shrinks one byte per char
  }
  
  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 '?'
  	}
  	m = Map(replaceNotLatin, "Hello\255World")
  	expect = "Hello?World"
  	if m != expect {
  		t.Errorf("replace invalid sequence: 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) }
  
  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"},
  	{"TrimRight", "abba", "a", "abb"},
  	{"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)
  			}
  		}
  	}
  }
  
  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, out string
  }{
  	{isSpace, space + " hello " + space, "hello"},
  	{isDigit, "\u0e50\u0e5212hello34\u0e50\u0e51", "hello"},
  	{isUpper, "\u2C6F\u2C6F\u2C6F\u2C6FABCDhelloEF\u2C6F\u2C6FGH\u2C6F\u2C6F", "hello"},
  	{not(isSpace), "hello" + space + "hello", space},
  	{not(isDigit), "hello\u0e50\u0e521234\u0e50\u0e51helo", "\u0e50\u0e521234\u0e50\u0e51"},
  	{isValidRune, "ab\xc0a\xc0cd", "\xc0a\xc0"},
  	{not(isValidRune), "\xc0a\xc0", "a"},
  }
  
  func TestTrimFunc(t *testing.T) {
  	for _, tc := range trimFuncTests {
  		actual := TrimFunc(tc.in, tc.f.f)
  		if actual != tc.out {
  			t.Errorf("TrimFunc(%q, %q) = %q; want %q", tc.in, tc.f.name, actual, tc.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)
  		}
  	}
  }
  
  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},
  }
  
  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)
  		}
  	}
  }
  
  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(\"%s\", \"%s\") = %d, want %d", tt.s, tt.sep, num, tt.num)
  		}
  	}
  }
  
  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) {
  	for i := 0; i < b.N; i++ {
  		Repeat("-", 80)
  	}
  }
  
  func BenchmarkIndexAnyASCII(b *testing.B) {
  	x := Repeat("#", 4096) // Never matches set
  	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) {
  				for i := 0; i < b.N; i++ {
  					IndexAny(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])
  				}
  			})
  		}
  	}
  }
  

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