diff --git a/util/stmtsummary/v2/stmtsummary.go b/util/stmtsummary/v2/stmtsummary.go
index d3a8c21c44751..13faffe65a0ea 100644
--- a/util/stmtsummary/v2/stmtsummary.go
+++ b/util/stmtsummary/v2/stmtsummary.go
@@ -367,25 +367,29 @@ func (s *StmtSummary) rotateLoop() {
 		case <-tick.C:
 			now := timeNow()
 			s.windowLock.Lock()
-			w := s.window
 			// The current window has expired and needs to be refreshed and persisted.
-			if now.After(w.begin.Add(time.Duration(s.RefreshInterval()) * time.Second)) {
-				s.window = newStmtWindow(now, uint(s.MaxStmtCount()))
-				size := w.lru.Size()
-				if size > 0 {
-					// Persist window asynchronously.
-					s.closeWg.Add(1)
-					go func() {
-						defer s.closeWg.Done()
-						s.storage.persist(w, now)
-					}()
-				}
+			if now.After(s.window.begin.Add(time.Duration(s.RefreshInterval()) * time.Second)) {
+				s.rotate(now)
 			}
 			s.windowLock.Unlock()
 		}
 	}
 }
 
+func (s *StmtSummary) rotate(now time.Time) {
+	w := s.window
+	s.window = newStmtWindow(now, uint(s.MaxStmtCount()))
+	size := w.lru.Size()
+	if size > 0 {
+		// Persist window asynchronously.
+		s.closeWg.Add(1)
+		go func() {
+			defer s.closeWg.Done()
+			s.storage.persist(w, now)
+		}()
+	}
+}
+
 // stmtWindow represents a single statistical window, which has a begin
 // time and an end time. Data within a single window is eliminated
 // according to the LRU strategy. All evicted data will be aggregated
diff --git a/util/stmtsummary/v2/stmtsummary_test.go b/util/stmtsummary/v2/stmtsummary_test.go
index a01d0143d4573..27e41f5283f4a 100644
--- a/util/stmtsummary/v2/stmtsummary_test.go
+++ b/util/stmtsummary/v2/stmtsummary_test.go
@@ -15,9 +15,7 @@
 package stmtsummary
 
 import (
-	"sync"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/require"
 )
@@ -47,7 +45,6 @@ func TestStmtSummary(t *testing.T) {
 	ss := NewStmtSummary4Test(3)
 	defer ss.Close()
 
-	ss.storage = &waitableMockStmtStorage{mockStmtStorage: ss.storage.(*mockStmtStorage)}
 	w := ss.window
 	ss.Add(GenerateStmtExecInfo4Test("digest1"))
 	ss.Add(GenerateStmtExecInfo4Test("digest2"))
@@ -57,14 +54,8 @@ func TestStmtSummary(t *testing.T) {
 	require.Equal(t, 3, w.lru.Size())
 	require.Equal(t, 2, w.evicted.count())
 
-	ss.storage.(*waitableMockStmtStorage).Add(1)
-	newEnd := w.begin.Add(time.Duration(ss.RefreshInterval()+1) * time.Second)
-	timeNow = func() time.Time {
-		return newEnd
-	}
-	ss.storage.(*waitableMockStmtStorage).Wait()
+	ss.rotate(timeNow())
 
-	timeNow = time.Now
 	ss.Add(GenerateStmtExecInfo4Test("digest6"))
 	ss.Add(GenerateStmtExecInfo4Test("digest7"))
 	w = ss.window
@@ -74,13 +65,3 @@ func TestStmtSummary(t *testing.T) {
 	ss.Clear()
 	require.Equal(t, 0, w.lru.Size())
 }
-
-type waitableMockStmtStorage struct {
-	sync.WaitGroup
-	*mockStmtStorage
-}
-
-func (s *waitableMockStmtStorage) persist(w *stmtWindow, end time.Time) {
-	defer s.Done()
-	s.mockStmtStorage.persist(w, end)
-}