// Copyright 2012 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"	"io/ioutil"	"os"	"strings"	"sync"	"testing") func TestReader(t *testing.T) {	r := strings.NewReader("0123456789")	tests := []struct {		off     int64		seek    int		n       int		want    string		wantpos int64		seekerr string	}{		{seek: os.SEEK_SET, off: 0, n: 20, want: "0123456789"},		{seek: os.SEEK_SET, off: 1, n: 1, want: "1"},		{seek: os.SEEK_CUR, off: 1, wantpos: 3, n: 2, want: "34"},		{seek: os.SEEK_SET, off: -1, seekerr: "strings.Reader.Seek: negative position"},		{seek: os.SEEK_SET, off: 1 << 33, wantpos: 1 << 33},		{seek: os.SEEK_CUR, off: 1, wantpos: 1<<33 + 1},		{seek: os.SEEK_SET, n: 5, want: "01234"},		{seek: os.SEEK_CUR, n: 5, want: "56789"},		{seek: os.SEEK_END, off: -1, n: 1, wantpos: 9, want: "9"},	} 	for i, tt := range tests {		pos, err := r.Seek(tt.off, tt.seek)		if err == nil && tt.seekerr != "" {			t.Errorf("%d. want seek error %q", i, tt.seekerr)			continue		}		if err != nil && err.Error() != tt.seekerr {			t.Errorf("%d. seek error = %q; want %q", i, err.Error(), tt.seekerr)			continue		}		if tt.wantpos != 0 && tt.wantpos != pos {			t.Errorf("%d. pos = %d, want %d", i, pos, tt.wantpos)		}		buf := make([]byte, tt.n)		n, err := r.Read(buf)		if err != nil {			t.Errorf("%d. read = %v", i, err)			continue		}		got := string(buf[:n])		if got != tt.want {			t.Errorf("%d. got %q; want %q", i, got, tt.want)		}	}} func TestReadAfterBigSeek(t *testing.T) {	r := strings.NewReader("0123456789")	if _, err := r.Seek(1<<31+5, os.SEEK_SET); err != nil {		t.Fatal(err)	}	if n, err := r.Read(make([]byte, 10)); n != 0 || err != io.EOF {		t.Errorf("Read = %d, %v; want 0, EOF", n, err)	}} func TestReaderAt(t *testing.T) {	r := strings.NewReader("0123456789")	tests := []struct {		off     int64		n       int		want    string		wanterr interface{}	}{		{0, 10, "0123456789", nil},		{1, 10, "123456789", io.EOF},		{1, 9, "123456789", nil},		{11, 10, "", io.EOF},		{0, 0, "", nil},		{-1, 0, "", "strings.Reader.ReadAt: negative offset"},	}	for i, tt := range tests {		b := make([]byte, tt.n)		rn, err := r.ReadAt(b, tt.off)		got := string(b[:rn])		if got != tt.want {			t.Errorf("%d. got %q; want %q", i, got, tt.want)		}		if fmt.Sprintf("%v", err) != fmt.Sprintf("%v", tt.wanterr) {			t.Errorf("%d. got error = %v; want %v", i, err, tt.wanterr)		}	}} func TestReaderAtConcurrent(t *testing.T) {	// Test for the race detector, to verify ReadAt doesn't mutate	// any state.	r := strings.NewReader("0123456789")	var wg sync.WaitGroup	for i := 0; i < 5; i++ {		wg.Add(1)		go func(i int) {			defer wg.Done()			var buf [1]byte			r.ReadAt(buf[:], int64(i))		}(i)	}	wg.Wait()} func TestEmptyReaderConcurrent(t *testing.T) {	// Test for the race detector, to verify a Read that doesn't yield any bytes	// is okay to use from multiple goroutines. This was our historic behavior.	// See golang.org/issue/7856	r := strings.NewReader("")	var wg sync.WaitGroup	for i := 0; i < 5; i++ {		wg.Add(2)		go func() {			defer wg.Done()			var buf [1]byte			r.Read(buf[:])		}()		go func() {			defer wg.Done()			r.Read(nil)		}()	}	wg.Wait()} func TestWriteTo(t *testing.T) {	const str = "0123456789"	for i := 0; i <= len(str); i++ {		s := str[i:]		r := strings.NewReader(s)		var b bytes.Buffer		n, err := r.WriteTo(&b)		if expect := int64(len(s)); n != expect {			t.Errorf("got %v; want %v", n, expect)		}		if err != nil {			t.Errorf("for length %d: got error = %v; want nil", len(s), err)		}		if b.String() != s {			t.Errorf("got string %q; want %q", b.String(), s)		}		if r.Len() != 0 {			t.Errorf("reader contains %v bytes; want 0", r.Len())		}	}} // tests that Len is affected by reads, but Size is not.func TestReaderLenSize(t *testing.T) {	r := strings.NewReader("abc")	io.CopyN(ioutil.Discard, r, 1)	if r.Len() != 2 {		t.Errorf("Len = %d; want 2", r.Len())	}	if r.Size() != 3 {		t.Errorf("Size = %d; want 3", r.Size())	}}