diff --git a/server/api/diagnostic_test.go b/server/api/diagnostic_test.go
index 3ff1cd20b22..f58360cc852 100644
--- a/server/api/diagnostic_test.go
+++ b/server/api/diagnostic_test.go
@@ -57,6 +57,7 @@ func (suite *diagnosticTestSuite) SetupSuite() {
 	mustBootstrapCluster(re, suite.svr)
 	mustPutStore(re, suite.svr, 1, metapb.StoreState_Up, metapb.NodeState_Serving, nil)
 	mustPutStore(re, suite.svr, 2, metapb.StoreState_Up, metapb.NodeState_Serving, nil)
+	suite.svr.GetRaftCluster().GetCoordinator().GetPrepareChecker().SetPrepared()
 }
 
 func (suite *diagnosticTestSuite) TearDownSuite() {
diff --git a/server/cluster/cluster_test.go b/server/cluster/cluster_test.go
index b2a7548eed9..8715419f36d 100644
--- a/server/cluster/cluster_test.go
+++ b/server/cluster/cluster_test.go
@@ -2989,6 +2989,8 @@ func TestScanLimit(t *testing.T) {
 func checkScanLimit(re *require.Assertions, regionCount int, expectScanLimit ...int) {
 	tc, co, cleanup := prepare(nil, nil, nil, re)
 	defer cleanup()
+	// set prepared to avoid prepare checker block the patrol
+	co.GetPrepareChecker().SetPrepared()
 	re.NoError(failpoint.Enable("github.com/tikv/pd/pkg/schedule/checker/breakPatrol", `return`))
 	re.NoError(failpoint.Enable("github.com/tikv/pd/pkg/schedule/checker/regionCount", fmt.Sprintf("return(\"%d\")", regionCount)))
 	defer func() {