Add unit test for mount error type

Author: hajiler

pkg/metrics/metrics.go

@@ -116,14 +116,9 @@ func (mm *MetricsManager) RecordOperationErrorMetrics(
 }
 
 func (mm *MetricsManager) RecordMountErrorMetric(fs_format string, err error) {
-	errType := "OK"
-	mntErr := &mount.MountError{}
-	if errors.As(err, mntErr) {
-		errType = string(mntErr.Type)
-	}
+	errType := mountErrorType(err)
 	mountErrorMetric.WithLabelValues(pdcsiDriverName, fs_format, errType).Inc()
-
-	klog.Infof("Recorded mount error type: %q", mntErr.Type)
+	klog.Infof("Recorded mount error type: %q", errType)
 }
 
 func (mm *MetricsManager) EmmitProcessStartTime() error {
@@ -198,3 +193,16 @@ func errorCodeLabelValue(operationErr error) string {
 	}
 	return err
 }
+
+func mountErrorType(err error) string {
+	if err == nil {
+		return "OK"
+	}
+
+	mntErr := &mount.MountError{}
+	if !errors.As(err, mntErr) {
+		return "UnknownError"
+	}
+
+	return string(mntErr.Type)
+}

pkg/metrics/metrics_test.go

@@ -29,6 +29,7 @@ import (
 	"google.golang.org/api/googleapi"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
+	"k8s.io/mount-utils"
 
 	"sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/common"
 	gce "sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/gce-cloud-provider/compute"
@@ -186,3 +187,35 @@ func TestErrorCodeLabelValue(t *testing.T) {
 		}
 	}
 }
+
+func TestMountOperationError(t *testing.T) {
+	testCases := []struct {
+		name string
+		err  error
+		want string
+	}{
+		{
+			name: "no error",
+			want: "OK",
+		},
+		{
+			name: "unknown error",
+			err:  fmt.Errorf("fake error"),
+			want: "UnknownError",
+		},
+		{
+			name: "mount error",
+			err:  mount.NewMountError(mount.FormatFailed, "file system format failed"),
+			want: string(mount.FormatFailed),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := mountErrorType(tc.err)
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("%s: -want err, +got err\n%s", tc.name, diff)
+			}
+		})
+	}
+}