tail_test.go - external/github.com/ActiveState/tail - Git at Google

 // Copyright (c) 2015 HPE Software Inc. All rights reserved.
 // Copyright (c) 2013 ActiveState Software Inc. All rights reserved.

 // TODO:
 //  * repeat all the tests with Poll:true

 package tail

 import (
 	_ "fmt"
 	"io/ioutil"
 	"os"
 	"strings"
 	"testing"
 	"time"

 	"github.com/hpcloud/tail/ratelimiter"
 	"github.com/hpcloud/tail/watch"
 )

 func init() {
 	// Clear the temporary test directory
 	err := os.RemoveAll(".test")
 	if err != nil {
 		panic(err)
 	}
 }

 func TestMain(m *testing.M) {
 	// Use a smaller poll duration for faster test runs. Keep it below
 	// 100ms (which value is used as common delays for tests)
 	watch.POLL_DURATION = 5 * time.Millisecond
 	os.Exit(m.Run())
 }

 func TestMustExist(t *testing.T) {
 	tail, err := TailFile("/no/such/file", Config{Follow: true, MustExist: true})
 	if err == nil {
 		t.Error("MustExist:true is violated")
 		tail.Stop()
 	}
 	tail, err = TailFile("/no/such/file", Config{Follow: true, MustExist: false})
 	if err != nil {
 		t.Error("MustExist:false is violated")
 	}
 	tail.Stop()
 	_, err = TailFile("README.md", Config{Follow: true, MustExist: true})
 	if err != nil {
 		t.Error("MustExist:true on an existing file is violated")
 	}
 	tail.Stop()
 	tail.Cleanup()
 }

 func TestStop(t *testing.T) {
 	tail, err := TailFile("_no_such_file", Config{Follow: true, MustExist: false})
 	if err != nil {
 		t.Error("MustExist:false is violated")
 	}
 	if tail.Stop() != nil {
 		t.Error("Should be stoped successfully")
 	}
 	tail.Cleanup()
 }

 func TestStopAtEOF(_t *testing.T) {
 	t := NewTailTest("maxlinesize", _t)
 	t.CreateFile("test.txt", "hello\nthere\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})

 	// read "hello"
 	<-tail.Lines

 	done := make(chan struct{})
 	go func() {
 		<-time.After(100 * time.Millisecond)
 		t.VerifyTailOutput(tail, []string{"there", "world"})
 		close(done)
 	}()
 	tail.StopAtEOF()
 	<-done
 	tail.Cleanup()
 }

 func MaxLineSizeT(_t *testing.T, follow bool, fileContent string, expected []string) {
 	t := NewTailTest("maxlinesize", _t)
 	t.CreateFile("test.txt", fileContent)
 	tail := t.StartTail("test.txt", Config{Follow: follow, Location: nil, MaxLineSize: 3})
 	go t.VerifyTailOutput(tail, expected)

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }

 func TestMaxLineSizeFollow(_t *testing.T) {
 	// As last file line does not end with newline, it will not be present in tail's output
 	MaxLineSizeT(_t, true, "hello\nworld\nfin\nhe", []string{"hel", "lo", "wor", "ld", "fin"})
 }

 func TestMaxLineSizeNoFollow(_t *testing.T) {
 	MaxLineSizeT(_t, false, "hello\nworld\nfin\nhe", []string{"hel", "lo", "wor", "ld", "fin", "he"})
 }

 func TestOver4096ByteLine(_t *testing.T) {
 	t := NewTailTest("Over4096ByteLine", _t)
 	testString := strings.Repeat("a", 4097)
 	t.CreateFile("test.txt", "test\n"+testString+"\nhello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
 	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }
 func TestOver4096ByteLineWithSetMaxLineSize(_t *testing.T) {
 	t := NewTailTest("Over4096ByteLineMaxLineSize", _t)
 	testString := strings.Repeat("a", 4097)
 	t.CreateFile("test.txt", "test\n"+testString+"\nhello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil, MaxLineSize: 4097})
 	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	// tail.Stop()
 	tail.Cleanup()
 }

 func TestLocationFull(_t *testing.T) {
 	t := NewTailTest("location-full", _t)
 	t.CreateFile("test.txt", "hello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
 	go t.VerifyTailOutput(tail, []string{"hello", "world"})

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }

 func TestLocationFullDontFollow(_t *testing.T) {
 	t := NewTailTest("location-full-dontfollow", _t)
 	t.CreateFile("test.txt", "hello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: false, Location: nil})
 	go t.VerifyTailOutput(tail, []string{"hello", "world"})

 	// Add more data only after reasonable delay.
 	<-time.After(100 * time.Millisecond)
 	t.AppendFile("test.txt", "more\ndata\n")
 	<-time.After(100 * time.Millisecond)

 	tail.Stop()
 	tail.Cleanup()
 }

 func TestLocationEnd(_t *testing.T) {
 	t := NewTailTest("location-end", _t)
 	t.CreateFile("test.txt", "hello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: &SeekInfo{0, os.SEEK_END}})
 	go t.VerifyTailOutput(tail, []string{"more", "data"})

 	<-time.After(100 * time.Millisecond)
 	t.AppendFile("test.txt", "more\ndata\n")

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }

 func TestLocationMiddle(_t *testing.T) {
 	// Test reading from middle.
 	t := NewTailTest("location-middle", _t)
 	t.CreateFile("test.txt", "hello\nworld\n")
 	tail := t.StartTail("test.txt", Config{Follow: true, Location: &SeekInfo{-6, os.SEEK_END}})
 	go t.VerifyTailOutput(tail, []string{"world", "more", "data"})

 	<-time.After(100 * time.Millisecond)
 	t.AppendFile("test.txt", "more\ndata\n")

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }

 func _TestReOpen(_t *testing.T, poll bool) {
 	var name string
 	var delay time.Duration
 	if poll {
 		name = "reopen-polling"
 		delay = 300 * time.Millisecond // account for POLL_DURATION
 	} else {
 		name = "reopen-inotify"
 		delay = 100 * time.Millisecond
 	}
 	t := NewTailTest(name, _t)
 	t.CreateFile("test.txt", "hello\nworld\n")
 	tail := t.StartTail(
 		"test.txt",
 		Config{Follow: true, ReOpen: true, Poll: poll})

 	go t.VerifyTailOutput(tail, []string{"hello", "world", "more", "data", "endofworld"})

 	// deletion must trigger reopen
 	<-time.After(delay)
 	t.RemoveFile("test.txt")
 	<-time.After(delay)
 	t.CreateFile("test.txt", "more\ndata\n")

 	// rename must trigger reopen
 	<-time.After(delay)
 	t.RenameFile("test.txt", "test.txt.rotated")
 	<-time.After(delay)
 	t.CreateFile("test.txt", "endofworld")

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(delay)
 	t.RemoveFile("test.txt")
 	<-time.After(delay)

 	// Do not bother with stopping as it could kill the tomb during
 	// the reading of data written above. Timings can vary based on
 	// test environment.
 	// tail.Stop()
 	tail.Cleanup()
 }

 // The use of polling file watcher could affect file rotation
 // (detected via renames), so test these explicitly.

 func TestReOpenInotify(_t *testing.T) {
 	_TestReOpen(_t, false)
 }

 func TestReOpenPolling(_t *testing.T) {
 	_TestReOpen(_t, true)
 }

 func _TestReSeek(_t *testing.T, poll bool) {
 	var name string
 	if poll {
 		name = "reseek-polling"
 	} else {
 		name = "reseek-inotify"
 	}
 	t := NewTailTest(name, _t)
 	t.CreateFile("test.txt", "a really long string goes here\nhello\nworld\n")
 	tail := t.StartTail(
 		"test.txt",
 		Config{Follow: true, ReOpen: false, Poll: poll})

 	go t.VerifyTailOutput(tail, []string{
 		"a really long string goes here", "hello", "world", "h311o", "w0r1d", "endofworld"})

 	// truncate now
 	<-time.After(100 * time.Millisecond)
 	t.TruncateFile("test.txt", "h311o\nw0r1d\nendofworld\n")

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")

 	// Do not bother with stopping as it could kill the tomb during
 	// the reading of data written above. Timings can vary based on
 	// test environment.
 	// tail.Stop()
 	tail.Cleanup()
 }

 // The use of polling file watcher could affect file rotation
 // (detected via renames), so test these explicitly.

 func TestReSeekInotify(_t *testing.T) {
 	_TestReSeek(_t, false)
 }

 func TestReSeekPolling(_t *testing.T) {
 	_TestReSeek(_t, true)
 }

 func TestRateLimiting(_t *testing.T) {
 	t := NewTailTest("rate-limiting", _t)
 	t.CreateFile("test.txt", "hello\nworld\nagain\nextra\n")
 	config := Config{
 		Follow:      true,
 		RateLimiter: ratelimiter.NewLeakyBucket(2, time.Second)}
 	leakybucketFull := "Too much log activity; waiting a second before resuming tailing"
 	tail := t.StartTail("test.txt", config)

 	// TODO: also verify that tail resumes after the cooloff period.
 	go t.VerifyTailOutput(tail, []string{
 		"hello", "world", "again",
 		leakybucketFull,
 		"more", "data",
 		leakybucketFull})

 	// Add more data only after reasonable delay.
 	<-time.After(1200 * time.Millisecond)
 	t.AppendFile("test.txt", "more\ndata\n")

 	// Delete after a reasonable delay, to give tail sufficient time
 	// to read all lines.
 	<-time.After(100 * time.Millisecond)
 	t.RemoveFile("test.txt")

 	// tail.Stop()
 	tail.Cleanup()
 }

 func TestTell(_t *testing.T) {
 	t := NewTailTest("tell-position", _t)
 	t.CreateFile("test.txt", "hello\nworld\nagain\nmore\n")
 	config := Config{
 		Follow:   false,
 		Location: &SeekInfo{0, os.SEEK_SET}}
 	tail := t.StartTail("test.txt", config)
 	// read noe line
 	<-tail.Lines
 	offset, err := tail.Tell()
 	if err != nil {
 		t.Errorf("Tell return error: %s", err.Error())
 	}
 	tail.Done()
 	// tail.close()

 	config = Config{
 		Follow:   false,
 		Location: &SeekInfo{offset, os.SEEK_SET}}
 	tail = t.StartTail("test.txt", config)
 	for l := range tail.Lines {
 		// it may readed one line in the chan(tail.Lines),
 		// so it may lost one line.
 		if l.Text != "world" && l.Text != "again" {
 			t.Fatalf("mismatch; expected world or again, but got %s",
 				l.Text)
 		}
 		break
 	}
 	t.RemoveFile("test.txt")
 	tail.Done()
 	tail.Cleanup()
 }

 func TestBlockUntilExists(_t *testing.T) {
 	t := NewTailTest("block-until-file-exists", _t)
 	config := Config{
 		Follow: true,
 	}
 	tail := t.StartTail("test.txt", config)
 	go func() {
 		time.Sleep(100 * time.Millisecond)
 		t.CreateFile("test.txt", "hello world\n")
 	}()
 	for l := range tail.Lines {
 		if l.Text != "hello world" {
 			t.Fatalf("mismatch; expected hello world, but got %s",
 				l.Text)
 		}
 		break
 	}
 	t.RemoveFile("test.txt")
 	tail.Stop()
 	tail.Cleanup()
 }

 // Test library

 type TailTest struct {
 	Name string
 	path string
 	*testing.T
 }

 func NewTailTest(name string, t *testing.T) TailTest {
 	tt := TailTest{name, ".test/" + name, t}
 	err := os.MkdirAll(tt.path, os.ModeTemporary|0700)
 	if err != nil {
 		tt.Fatal(err)
 	}

 	return tt
 }

 func (t TailTest) CreateFile(name string, contents string) {
 	err := ioutil.WriteFile(t.path+"/"+name, []byte(contents), 0600)
 	if err != nil {
 		t.Fatal(err)
 	}
 }

 func (t TailTest) RemoveFile(name string) {
 	err := os.Remove(t.path + "/" + name)
 	if err != nil {
 		t.Fatal(err)
 	}
 }

 func (t TailTest) RenameFile(oldname string, newname string) {
 	oldname = t.path + "/" + oldname
 	newname = t.path + "/" + newname
 	err := os.Rename(oldname, newname)
 	if err != nil {
 		t.Fatal(err)
 	}
 }

 func (t TailTest) AppendFile(name string, contents string) {
 	f, err := os.OpenFile(t.path+"/"+name, os.O_APPEND|os.O_WRONLY, 0600)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
 	_, err = f.WriteString(contents)
 	if err != nil {
 		t.Fatal(err)
 	}
 }

 func (t TailTest) TruncateFile(name string, contents string) {
 	f, err := os.OpenFile(t.path+"/"+name, os.O_TRUNC|os.O_WRONLY, 0600)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer f.Close()
 	_, err = f.WriteString(contents)
 	if err != nil {
 		t.Fatal(err)
 	}
 }

 func (t TailTest) StartTail(name string, config Config) *Tail {
 	tail, err := TailFile(t.path+"/"+name, config)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return tail
 }

 func (t TailTest) VerifyTailOutput(tail *Tail, lines []string) {
 	for idx, line := range lines {
 		tailedLine, ok := <-tail.Lines
 		if !ok {
 			// tail.Lines is closed and empty.
 			err := tail.Err()
 			if err != nil {
 				t.Fatalf("tail ended with error: %v", err)
 			}
 			t.Fatalf("tail ended early; expecting more: %v", lines[idx:])
 		}
 		if tailedLine == nil {
 			t.Fatalf("tail.Lines returned nil; not possible")
 		}
 		// Note: not checking .Err as the `lines` argument is designed
 		// to match error strings as well.
 		if tailedLine.Text != line {
 			t.Fatalf(
 				"unexpected line/err from tail: "+
 					"expecting <<%s>>>, but got <<<%s>>>",
 				line, tailedLine.Text)
 		}
 	}
 	line, ok := <-tail.Lines
 	if ok {
 		t.Fatalf("more content from tail: %+v", line)
 	}
 }
	// Copyright (c) 2015 HPE Software Inc. All rights reserved.
	// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.

	// TODO:
	// * repeat all the tests with Poll:true

	package tail

	import (
	_ "fmt"
	"io/ioutil"
	"os"
	"strings"
	"testing"
	"time"

	"github.com/hpcloud/tail/ratelimiter"
	"github.com/hpcloud/tail/watch"
	)

	func init() {
	// Clear the temporary test directory
	err := os.RemoveAll(".test")
	if err != nil {
	panic(err)
	}
	}

	func TestMain(m *testing.M) {
	// Use a smaller poll duration for faster test runs. Keep it below
	// 100ms (which value is used as common delays for tests)
	watch.POLL_DURATION = 5 * time.Millisecond
	os.Exit(m.Run())
	}

	func TestMustExist(t *testing.T) {
	tail, err := TailFile("/no/such/file", Config{Follow: true, MustExist: true})
	if err == nil {
	t.Error("MustExist:true is violated")
	tail.Stop()
	}
	tail, err = TailFile("/no/such/file", Config{Follow: true, MustExist: false})
	if err != nil {
	t.Error("MustExist:false is violated")
	}
	tail.Stop()
	_, err = TailFile("README.md", Config{Follow: true, MustExist: true})
	if err != nil {
	t.Error("MustExist:true on an existing file is violated")
	}
	tail.Stop()
	tail.Cleanup()
	}

	func TestStop(t *testing.T) {
	tail, err := TailFile("_no_such_file", Config{Follow: true, MustExist: false})
	if err != nil {
	t.Error("MustExist:false is violated")
	}
	if tail.Stop() != nil {
	t.Error("Should be stoped successfully")
	}
	tail.Cleanup()
	}

	func TestStopAtEOF(_t *testing.T) {
	t := NewTailTest("maxlinesize", _t)
	t.CreateFile("test.txt", "hello\nthere\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})

	// read "hello"
	<-tail.Lines

	done := make(chan struct{})
	go func() {
	<-time.After(100 * time.Millisecond)
	t.VerifyTailOutput(tail, []string{"there", "world"})
	close(done)
	}()
	tail.StopAtEOF()
	<-done
	tail.Cleanup()
	}

	func MaxLineSizeT(_t *testing.T, follow bool, fileContent string, expected []string) {
	t := NewTailTest("maxlinesize", _t)
	t.CreateFile("test.txt", fileContent)
	tail := t.StartTail("test.txt", Config{Follow: follow, Location: nil, MaxLineSize: 3})
	go t.VerifyTailOutput(tail, expected)

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}

	func TestMaxLineSizeFollow(_t *testing.T) {
	// As last file line does not end with newline, it will not be present in tail's output
	MaxLineSizeT(_t, true, "hello\nworld\nfin\nhe", []string{"hel", "lo", "wor", "ld", "fin"})
	}

	func TestMaxLineSizeNoFollow(_t *testing.T) {
	MaxLineSizeT(_t, false, "hello\nworld\nfin\nhe", []string{"hel", "lo", "wor", "ld", "fin", "he"})
	}

	func TestOver4096ByteLine(_t *testing.T) {
	t := NewTailTest("Over4096ByteLine", _t)
	testString := strings.Repeat("a", 4097)
	t.CreateFile("test.txt", "test\n"+testString+"\nhello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}
	func TestOver4096ByteLineWithSetMaxLineSize(_t *testing.T) {
	t := NewTailTest("Over4096ByteLineMaxLineSize", _t)
	testString := strings.Repeat("a", 4097)
	t.CreateFile("test.txt", "test\n"+testString+"\nhello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil, MaxLineSize: 4097})
	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	// tail.Stop()
	tail.Cleanup()
	}

	func TestLocationFull(_t *testing.T) {
	t := NewTailTest("location-full", _t)
	t.CreateFile("test.txt", "hello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
	go t.VerifyTailOutput(tail, []string{"hello", "world"})

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}

	func TestLocationFullDontFollow(_t *testing.T) {
	t := NewTailTest("location-full-dontfollow", _t)
	t.CreateFile("test.txt", "hello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: false, Location: nil})
	go t.VerifyTailOutput(tail, []string{"hello", "world"})

	// Add more data only after reasonable delay.
	<-time.After(100 * time.Millisecond)
	t.AppendFile("test.txt", "more\ndata\n")
	<-time.After(100 * time.Millisecond)

	tail.Stop()
	tail.Cleanup()
	}

	func TestLocationEnd(_t *testing.T) {
	t := NewTailTest("location-end", _t)
	t.CreateFile("test.txt", "hello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: &SeekInfo{0, os.SEEK_END}})
	go t.VerifyTailOutput(tail, []string{"more", "data"})

	<-time.After(100 * time.Millisecond)
	t.AppendFile("test.txt", "more\ndata\n")

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}

	func TestLocationMiddle(_t *testing.T) {
	// Test reading from middle.
	t := NewTailTest("location-middle", _t)
	t.CreateFile("test.txt", "hello\nworld\n")
	tail := t.StartTail("test.txt", Config{Follow: true, Location: &SeekInfo{-6, os.SEEK_END}})
	go t.VerifyTailOutput(tail, []string{"world", "more", "data"})

	<-time.After(100 * time.Millisecond)
	t.AppendFile("test.txt", "more\ndata\n")

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}

	func _TestReOpen(_t *testing.T, poll bool) {
	var name string
	var delay time.Duration
	if poll {
	name = "reopen-polling"
	delay = 300 * time.Millisecond // account for POLL_DURATION
	} else {
	name = "reopen-inotify"
	delay = 100 * time.Millisecond
	}
	t := NewTailTest(name, _t)
	t.CreateFile("test.txt", "hello\nworld\n")
	tail := t.StartTail(
	"test.txt",
	Config{Follow: true, ReOpen: true, Poll: poll})

	go t.VerifyTailOutput(tail, []string{"hello", "world", "more", "data", "endofworld"})

	// deletion must trigger reopen
	<-time.After(delay)
	t.RemoveFile("test.txt")
	<-time.After(delay)
	t.CreateFile("test.txt", "more\ndata\n")

	// rename must trigger reopen
	<-time.After(delay)
	t.RenameFile("test.txt", "test.txt.rotated")
	<-time.After(delay)
	t.CreateFile("test.txt", "endofworld")

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(delay)
	t.RemoveFile("test.txt")
	<-time.After(delay)

	// Do not bother with stopping as it could kill the tomb during
	// the reading of data written above. Timings can vary based on
	// test environment.
	// tail.Stop()
	tail.Cleanup()
	}

	// The use of polling file watcher could affect file rotation
	// (detected via renames), so test these explicitly.

	func TestReOpenInotify(_t *testing.T) {
	_TestReOpen(_t, false)
	}

	func TestReOpenPolling(_t *testing.T) {
	_TestReOpen(_t, true)
	}

	func _TestReSeek(_t *testing.T, poll bool) {
	var name string
	if poll {
	name = "reseek-polling"
	} else {
	name = "reseek-inotify"
	}
	t := NewTailTest(name, _t)
	t.CreateFile("test.txt", "a really long string goes here\nhello\nworld\n")
	tail := t.StartTail(
	"test.txt",
	Config{Follow: true, ReOpen: false, Poll: poll})

	go t.VerifyTailOutput(tail, []string{
	"a really long string goes here", "hello", "world", "h311o", "w0r1d", "endofworld"})

	// truncate now
	<-time.After(100 * time.Millisecond)
	t.TruncateFile("test.txt", "h311o\nw0r1d\nendofworld\n")

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")

	// Do not bother with stopping as it could kill the tomb during
	// the reading of data written above. Timings can vary based on
	// test environment.
	// tail.Stop()
	tail.Cleanup()
	}

	// The use of polling file watcher could affect file rotation
	// (detected via renames), so test these explicitly.

	func TestReSeekInotify(_t *testing.T) {
	_TestReSeek(_t, false)
	}

	func TestReSeekPolling(_t *testing.T) {
	_TestReSeek(_t, true)
	}

	func TestRateLimiting(_t *testing.T) {
	t := NewTailTest("rate-limiting", _t)
	t.CreateFile("test.txt", "hello\nworld\nagain\nextra\n")
	config := Config{
	Follow: true,
	RateLimiter: ratelimiter.NewLeakyBucket(2, time.Second)}
	leakybucketFull := "Too much log activity; waiting a second before resuming tailing"
	tail := t.StartTail("test.txt", config)

	// TODO: also verify that tail resumes after the cooloff period.
	go t.VerifyTailOutput(tail, []string{
	"hello", "world", "again",
	leakybucketFull,
	"more", "data",
	leakybucketFull})

	// Add more data only after reasonable delay.
	<-time.After(1200 * time.Millisecond)
	t.AppendFile("test.txt", "more\ndata\n")

	// Delete after a reasonable delay, to give tail sufficient time
	// to read all lines.
	<-time.After(100 * time.Millisecond)
	t.RemoveFile("test.txt")

	// tail.Stop()
	tail.Cleanup()
	}

	func TestTell(_t *testing.T) {
	t := NewTailTest("tell-position", _t)
	t.CreateFile("test.txt", "hello\nworld\nagain\nmore\n")
	config := Config{
	Follow: false,
	Location: &SeekInfo{0, os.SEEK_SET}}
	tail := t.StartTail("test.txt", config)
	// read noe line
	<-tail.Lines
	offset, err := tail.Tell()
	if err != nil {
	t.Errorf("Tell return error: %s", err.Error())
	}
	tail.Done()
	// tail.close()

	config = Config{
	Follow: false,
	Location: &SeekInfo{offset, os.SEEK_SET}}
	tail = t.StartTail("test.txt", config)
	for l := range tail.Lines {
	// it may readed one line in the chan(tail.Lines),
	// so it may lost one line.
	if l.Text != "world" && l.Text != "again" {
	t.Fatalf("mismatch; expected world or again, but got %s",
	l.Text)
	}
	break
	}
	t.RemoveFile("test.txt")
	tail.Done()
	tail.Cleanup()
	}

	func TestBlockUntilExists(_t *testing.T) {
	t := NewTailTest("block-until-file-exists", _t)
	config := Config{
	Follow: true,
	}
	tail := t.StartTail("test.txt", config)
	go func() {
	time.Sleep(100 * time.Millisecond)
	t.CreateFile("test.txt", "hello world\n")
	}()
	for l := range tail.Lines {
	if l.Text != "hello world" {
	t.Fatalf("mismatch; expected hello world, but got %s",
	l.Text)
	}
	break
	}
	t.RemoveFile("test.txt")
	tail.Stop()
	tail.Cleanup()
	}

	// Test library

	type TailTest struct {
	Name string
	path string
	*testing.T
	}

	func NewTailTest(name string, t *testing.T) TailTest {
	tt := TailTest{name, ".test/" + name, t}
	err := os.MkdirAll(tt.path, os.ModeTemporary\|0700)
	if err != nil {
	tt.Fatal(err)
	}

	return tt
	}

	func (t TailTest) CreateFile(name string, contents string) {
	err := ioutil.WriteFile(t.path+"/"+name, []byte(contents), 0600)
	if err != nil {
	t.Fatal(err)
	}
	}

	func (t TailTest) RemoveFile(name string) {
	err := os.Remove(t.path + "/" + name)
	if err != nil {
	t.Fatal(err)
	}
	}

	func (t TailTest) RenameFile(oldname string, newname string) {
	oldname = t.path + "/" + oldname
	newname = t.path + "/" + newname
	err := os.Rename(oldname, newname)
	if err != nil {
	t.Fatal(err)
	}
	}

	func (t TailTest) AppendFile(name string, contents string) {
	f, err := os.OpenFile(t.path+"/"+name, os.O_APPEND\|os.O_WRONLY, 0600)
	if err != nil {
	t.Fatal(err)
	}
	defer f.Close()
	_, err = f.WriteString(contents)
	if err != nil {
	t.Fatal(err)
	}
	}

	func (t TailTest) TruncateFile(name string, contents string) {
	f, err := os.OpenFile(t.path+"/"+name, os.O_TRUNC\|os.O_WRONLY, 0600)
	if err != nil {
	t.Fatal(err)
	}
	defer f.Close()
	_, err = f.WriteString(contents)
	if err != nil {
	t.Fatal(err)
	}
	}

	func (t TailTest) StartTail(name string, config Config) *Tail {
	tail, err := TailFile(t.path+"/"+name, config)
	if err != nil {
	t.Fatal(err)
	}
	return tail
	}

	func (t TailTest) VerifyTailOutput(tail *Tail, lines []string) {
	for idx, line := range lines {
	tailedLine, ok := <-tail.Lines
	if !ok {
	// tail.Lines is closed and empty.
	err := tail.Err()
	if err != nil {
	t.Fatalf("tail ended with error: %v", err)
	}
	t.Fatalf("tail ended early; expecting more: %v", lines[idx:])
	}
	if tailedLine == nil {
	t.Fatalf("tail.Lines returned nil; not possible")
	}
	// Note: not checking .Err as the `lines` argument is designed
	// to match error strings as well.
	if tailedLine.Text != line {
	t.Fatalf(
	"unexpected line/err from tail: "+
	"expecting <<%s>>>, but got <<<%s>>>",
	line, tailedLine.Text)
	}
	}
	line, ok := <-tail.Lines
	if ok {
	t.Fatalf("more content from tail: %+v", line)
	}
	}