diff --git a/test/instrumentation/decode_metric.go b/test/instrumentation/decode_metric.go
index 81bb878c4b3..4ceeda7b516 100644
--- a/test/instrumentation/decode_metric.go
+++ b/test/instrumentation/decode_metric.go
@@ -70,7 +70,7 @@ func (c *metricDecoder) decodeNewMetricCall(fc *ast.CallExpr) (*metric, error) {
 		return nil, nil
 	}
 	switch functionName {
-	case "NewCounter", "NewGauge", "NewHistogram", "NewSummary", "NewTimingHistogram":
+	case "NewCounter", "NewGauge", "NewHistogram", "NewSummary", "NewTimingHistogram", "NewGaugeFunc":
 		m, err = c.decodeMetric(fc)
 	case "NewCounterVec", "NewGaugeVec", "NewHistogramVec", "NewSummaryVec", "NewTimingHistogramVec":
 		m, err = c.decodeMetricVec(fc)
@@ -90,7 +90,7 @@ func getMetricType(functionName string) string {
 	switch functionName {
 	case "NewCounter", "NewCounterVec":
 		return counterMetricType
-	case "NewGauge", "NewGaugeVec":
+	case "NewGauge", "NewGaugeVec", "NewGaugeFunc":
 		return gaugeMetricType
 	case "NewHistogram", "NewHistogramVec":
 		return histogramMetricType
@@ -104,7 +104,7 @@ func getMetricType(functionName string) string {
 }
 
 func (c *metricDecoder) decodeMetric(call *ast.CallExpr) (metric, error) {
-	if len(call.Args) != 1 {
+	if len(call.Args) > 2 {
 		return metric{}, newDecodeErrorf(call, errInvalidNewMetricCall)
 	}
 	return c.decodeOpts(call.Args[0])
diff --git a/test/instrumentation/testdata/pkg/kubelet/metrics/metrics.go b/test/instrumentation/testdata/pkg/kubelet/metrics/metrics.go
index 45bbe077938..da29941fb30 100644
--- a/test/instrumentation/testdata/pkg/kubelet/metrics/metrics.go
+++ b/test/instrumentation/testdata/pkg/kubelet/metrics/metrics.go
@@ -481,6 +481,20 @@ func Register(collectors ...metrics.StableCollector) {
 		for _, collector := range collectors {
 			legacyregistry.CustomMustRegister(collector)
 		}
+		legacyregistry.RawMustRegister(metrics.NewGaugeFunc(
+			&metrics.GaugeOpts{
+				Subsystem: "kubelet",
+				Name:      "certificate_manager_client_ttl_seconds",
+				Help: "Gauge of the TTL (time-to-live) of the Kubelet's client certificate. " +
+					"The value is in seconds until certificate expiry (negative if already expired). " +
+					"If client certificate is invalid or unused, the value will be +INF.",
+				StabilityLevel: metrics.BETA,
+			},
+			func() float64 {
+				return 0
+			},
+		))
+
 	})
 }
 
diff --git a/test/instrumentation/testdata/test-stable-metrics-list.yaml b/test/instrumentation/testdata/test-stable-metrics-list.yaml
index 4fbe7ee07c1..668daa62d7b 100644
--- a/test/instrumentation/testdata/test-stable-metrics-list.yaml
+++ b/test/instrumentation/testdata/test-stable-metrics-list.yaml
@@ -1,3 +1,10 @@
+- name: certificate_manager_client_ttl_seconds
+  subsystem: kubelet
+  help: Gauge of the TTL (time-to-live) of the Kubelet's client certificate. The value
+    is in seconds until certificate expiry (negative if already expired). If client
+    certificate is invalid or unused, the value will be +INF.
+  type: Gauge
+  stabilityLevel: BETA
 - name: device_plugin_alloc_duration_seconds
   subsystem: kubelet
   help: Duration in seconds to serve a device plugin Allocation request. Broken down