diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 8e77867ad..504f3e64c 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -105,7 +105,9 @@ jobs:
       - name: Run Go test
         run: make test
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v2
+        uses: codecov/codecov-action@v3
         with:
           flags: unittests
           file: cover.out
+          fail_ci_if_error: true
+          verbose: true
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 000000000..75269b9bc
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,17 @@
+flag_management:
+  default_rules:
+    carryforward: true
+    statuses:
+      - name_prefix: project-
+        type: project
+        target: auto
+        threshold: 5%
+        if_no_uploads: error
+        if_not_found: success # no commit found? still set a success
+      - name_prefix: patch-
+        type: patch
+        target: 70%
+        if_no_uploads: success
+        if_not_found: success
+github_checks:
+  annotations: true
diff --git a/pkg/util/pod.go b/pkg/util/pod.go
index d5ec24a01..3dd5543c8 100644
--- a/pkg/util/pod.go
+++ b/pkg/util/pod.go
@@ -95,7 +95,7 @@ func GetPodCgroupCPUStatPath(podParentDir string) string {
 
 func GetKubeQosClass(pod *corev1.Pod) corev1.PodQOSClass {
 	qosClass := pod.Status.QOSClass
-	if qosClass == "" {
+	if len(qosClass) <= 0 {
 		qosClass = qos.GetPodQOS(pod)
 	}
 	return qosClass
diff --git a/pkg/util/stat_test.go b/pkg/util/stat_test.go
index 9aa5413b2..68acf575d 100644
--- a/pkg/util/stat_test.go
+++ b/pkg/util/stat_test.go
@@ -18,6 +18,7 @@ package util
 
 import (
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"runtime"
 	"testing"
@@ -98,11 +99,14 @@ func Test_readPodCPUStatUsageTicks(t *testing.T) {
 	tempDir := t.TempDir()
 	tempInvalidPodCgroupDir := filepath.Join(tempDir, "no_cgroup")
 	tempPodStatPath := filepath.Join(tempDir, system.CpuacctStatFileName)
-	statContentStr := getStatContents()
-	err := ioutil.WriteFile(tempPodStatPath, []byte(statContentStr), 0666)
-	if err != nil {
-		t.Error(err)
-	}
+	err := ioutil.WriteFile(tempPodStatPath, []byte(getStatContents()), 0666)
+	assert.NoError(t, err)
+	tempInvalidPodCgroupDir1 := filepath.Join(tempDir, "no_cgroup_1")
+	err = os.Mkdir(tempInvalidPodCgroupDir1, 0755)
+	assert.NoError(t, err)
+	tempPodInvalidStatPath := filepath.Join(tempInvalidPodCgroupDir1, system.CpuacctStatFileName)
+	err = ioutil.WriteFile(tempPodInvalidStatPath, []byte(getInvalidStatContents()), 0666)
+	assert.NoError(t, err)
 	type args struct {
 		podCgroupDir string
 	}
@@ -124,16 +128,18 @@ func Test_readPodCPUStatUsageTicks(t *testing.T) {
 			want:    1356232,
 			wantErr: false,
 		},
+		{
+			name:    "read invalid cpu stat content",
+			args:    args{podCgroupDir: tempPodInvalidStatPath},
+			want:    0,
+			wantErr: true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			got, err := readCPUAcctStatUsageTicks(tt.args.podCgroupDir)
-			if (err != nil) != tt.wantErr {
-				t.Errorf("readCPUAcctStatUsageTicks wantErr %v but got err %s", tt.wantErr, err)
-			}
-			if !tt.wantErr && got != tt.want {
-				t.Errorf("readCPUAcctStatUsageTicks want %v but got %v", tt.want, got)
-			}
+			assert.Equal(t, tt.wantErr, err != nil)
+			assert.Equal(t, tt.want, got)
 		})
 	}
 }
@@ -151,6 +157,12 @@ func getStatContents() string {
 		"nr_running 0\nnr_uninterrupible 0\nnr_switches 234453363\n"
 }
 
+func getInvalidStatContents() string {
+	return "user 407232\nnice a\nsystem a\nidle a\niowait a\nirq 0\nsoftirq 0\n" +
+		"steal 1115801\nguest 0\nload average(1min) 5\nload average(5min) 1\nload average(15min) 0\n" +
+		"nr_running 0\nnr_uninterrupible 0\nnr_switches 234453363\n"
+}
+
 func TestGetContainerCPUStatUsageTicks(t *testing.T) {
 	helper := system.NewFileTestUtil(t)
 	podCgroupDir := "pod-cgroup-dir"