diff --git a/pump/storage/chaser.go b/pump/storage/chaser.go
index d867081d7..7074ed05d 100644
--- a/pump/storage/chaser.go
+++ b/pump/storage/chaser.go
@@ -29,9 +29,13 @@ var (
 	recoveryCoolDown     = time.Minute
 )
 
+type valLogScanner interface {
+	scanRequests(valuePointer, func(*request) error) error
+}
+
 type slowChaser struct {
 	on                 int32
-	vlog               *valueLog
+	vlog               valLogScanner
 	lastUnreadPtr      *valuePointer
 	recoveryTimeout    time.Duration
 	lastRecoverAttempt time.Time
@@ -39,7 +43,7 @@ type slowChaser struct {
 	WriteLock          sync.Mutex
 }
 
-func newSlowChaser(vlog *valueLog, recoveryTimeout time.Duration, output chan *request) *slowChaser {
+func newSlowChaser(vlog valLogScanner, recoveryTimeout time.Duration, output chan *request) *slowChaser {
 	return &slowChaser{
 		recoveryTimeout: recoveryTimeout,
 		vlog:            vlog,
diff --git a/pump/storage/chaser_test.go b/pump/storage/chaser_test.go
index d1c2e9c1d..3e0333c4f 100644
--- a/pump/storage/chaser_test.go
+++ b/pump/storage/chaser_test.go
@@ -18,8 +18,17 @@ import (
 	"time"
 
 	. "github.com/pingcap/check"
+	"github.com/pingcap/errors"
 )
 
+type scannerMock struct {
+	scanImpl func(valuePointer, func(*request) error) error
+}
+
+func (sm scannerMock) scanRequests(start valuePointer, f func(*request) error) error {
+	return sm.scanImpl(start, f)
+}
+
 type waitUntilTurnedOnSuite struct{}
 
 var _ = Suite(&waitUntilTurnedOnSuite{})
@@ -68,18 +77,180 @@ type runSuite struct{}
 
 var _ = Suite(&runSuite{})
 
-func (rs *runSuite) TestCanBeStoppedWhenWaiting(c *C) {
-	sc := slowChaser{}
-	ctx, cancel := context.WithCancel(context.Background())
+func (rs *runSuite) managedRun(ctx context.Context, c *C, sc *slowChaser) {
 	stopped := make(chan struct{})
 	go func() {
 		sc.Run(ctx)
 		close(stopped)
 	}()
-	cancel()
 	select {
 	case <-stopped:
 	case <-time.After(500 * time.Millisecond):
-		c.Fatal("Takes too long to stop slow chaser")
+		c.Fatal("Run doesn't return in time after canceled.")
+	}
+}
+
+func (rs *runSuite) TestCanBeStoppedWhenWaiting(c *C) {
+	sc := slowChaser{}
+	ctx, cancel := context.WithCancel(context.Background())
+	go cancel()
+	rs.managedRun(ctx, c, &sc)
+}
+
+func (rs *runSuite) TestShouldRetryIfFailedToCatchUp(c *C) {
+	mock := struct{ scannerMock }{}
+	var offsetRecords []valuePointer
+	finished := make(chan struct{})
+	mock.scanImpl = func(start valuePointer, f func(*request) error) error {
+		offsetRecords = append(offsetRecords, start)
+		for i := 0; i < 3; i++ {
+			next := request{
+				valuePointer: valuePointer{
+					Fid:    start.Fid,
+					Offset: start.Offset + int64(i*10),
+				},
+			}
+			f(&next)
+		}
+		if len(offsetRecords) == 3 {
+			close(finished)
+		}
+		return errors.New("fake")
 	}
+	sc := newSlowChaser(mock, time.Second, make(chan *request, 100))
+	sc.TurnOn(&valuePointer{Fid: 42, Offset: 1000})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-finished
+		cancel()
+
+		c.Assert(len(offsetRecords), GreaterEqual, 3)
+		c.Assert(offsetRecords[0], DeepEquals, valuePointer{Fid: 42, Offset: 1000})
+		c.Assert(offsetRecords[1], DeepEquals, valuePointer{Fid: 42, Offset: 1020})
+		c.Assert(offsetRecords[2], DeepEquals, valuePointer{Fid: 42, Offset: 1040})
+	}()
+
+	rs.managedRun(ctx, c, sc)
+}
+
+func (rs *runSuite) TestShouldNotTryRecoveryForSlowCatchUp(c *C) {
+	mock := struct{ scannerMock }{}
+	callCount := 0
+	finished := make(chan struct{})
+	mock.scanImpl = func(start valuePointer, f func(*request) error) error {
+		callCount++
+		if callCount == 3 {
+			close(finished)
+		}
+		time.Sleep(time.Millisecond)
+		return nil
+	}
+
+	sc := newSlowChaser(mock, time.Second, make(chan *request, 100))
+	sc.TurnOn(&valuePointer{Fid: 42, Offset: 1000})
+
+	// Make sure lastRecoverAttempt is not set
+	c.Assert(sc.lastRecoverAttempt, Equals, time.Time{})
+
+	origThres := slowCatchUpThreshold
+	defer func() {
+		slowCatchUpThreshold = origThres
+	}()
+	// Set threshold to be 0.5ms which is smaller than 1ms
+	slowCatchUpThreshold = 500 * time.Microsecond
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-finished
+		cancel()
+		c.Assert(sc.lastRecoverAttempt, Equals, time.Time{})
+		c.Assert(sc.IsOn(), IsTrue)
+	}()
+
+	rs.managedRun(ctx, c, sc)
+}
+
+func (rs *runSuite) TestShouldNotRecoverFrequently(c *C) {
+	mock := struct{ scannerMock }{}
+	callCount := 0
+	finished := make(chan struct{})
+	mock.scanImpl = func(start valuePointer, f func(*request) error) error {
+		callCount++
+		if callCount == 3 {
+			close(finished)
+		}
+		return nil
+	}
+
+	sc := newSlowChaser(mock, time.Second, make(chan *request, 100))
+	sc.TurnOn(&valuePointer{Fid: 42, Offset: 1000})
+
+	// Set it up like we have just tried recovering and failed
+	sc.lastRecoverAttempt = time.Now()
+	lastRecoverAttempt := sc.lastRecoverAttempt
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-finished
+		cancel()
+		c.Assert(sc.lastRecoverAttempt, Equals, lastRecoverAttempt)
+		c.Assert(sc.IsOn(), IsTrue)
+	}()
+
+	rs.managedRun(ctx, c, sc)
+}
+
+func (rs *runSuite) TestShouldRecoverAndTurnOff(c *C) {
+	mock := struct{ scannerMock }{}
+	callCount := 0
+	finished := make(chan struct{})
+	mock.scanImpl = func(start valuePointer, f func(*request) error) error {
+		callCount++
+		// Should be called 2 times: catch up and recover
+		if callCount == 2 {
+			close(finished)
+		}
+		return nil
+	}
+
+	sc := newSlowChaser(mock, time.Second, make(chan *request, 100))
+	sc.TurnOn(&valuePointer{Fid: 42, Offset: 1000})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-finished
+		cancel()
+	}()
+	rs.managedRun(ctx, c, sc)
+	c.Assert(sc.IsOn(), IsFalse)
+}
+
+func (rs *runSuite) TestContinueCatchingUpIfRecoveryFailed(c *C) {
+	mock := struct{ scannerMock }{}
+	callCount := 0
+	finished := make(chan struct{})
+	mock.scanImpl = func(start valuePointer, f func(*request) error) error {
+		callCount++
+		// Arrange for at least 3 calls: catch up, failed-recovery, catch up
+		if callCount == 3 {
+			close(finished)
+		}
+		if callCount == 2 {
+			return errors.New("Failed recovery")
+		}
+		return nil
+	}
+
+	sc := newSlowChaser(mock, time.Second, make(chan *request, 100))
+	sc.TurnOn(&valuePointer{Fid: 42, Offset: 1000})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-finished
+		cancel()
+	}()
+
+	rs.managedRun(ctx, c, sc)
+	c.Assert(sc.IsOn(), IsTrue)
 }