e2e: eg controlplane metrics

Signed-off-by: zirain <zirain2009@gmail.com>

test/e2e/testdata/prometheus.yaml

@@ -0,0 +1,16 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: envoy-gateway-lb
+  namespace: envoy-gateway-system
+  labels:
+    control-plane: envoy-gateway
+spec:
+  selector:
+    control-plane: envoy-gateway
+  ports:
+    - name: http-metrics
+      port: 19001
+      protocol: TCP
+      targetPort: 19001
+  type: LoadBalancer

test/e2e/tests/prometheus.go

@@ -0,0 +1,46 @@
+// Copyright Envoy Gateway Authors
+// SPDX-License-Identifier: Apache-2.0
+// The full text of the Apache license is available in the LICENSE file at
+// the root of the repo.
+
+//go:build e2e
+// +build e2e
+
+package tests
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"sigs.k8s.io/gateway-api/conformance/utils/suite"
+)
+
+func init() {
+	ConformanceTests = append(ConformanceTests, PrometheusTest)
+}
+
+var PrometheusTest = suite.ConformanceTest{
+	ShortName:   "Prometheus",
+	Description: "Make sure Prometheus endpoint is working",
+	Manifests:   []string{"testdata/prometheus.yaml"},
+	Test: func(t *testing.T, suite *suite.ConformanceTestSuite) {
+		t.Run("MetricExists", func(t *testing.T) {
+			if err := wait.PollUntilContextTimeout(context.TODO(), time.Second, time.Minute, true,
+				func(_ context.Context) (done bool, err error) {
+					if err := ScrapeMetrics(t, suite.Client, types.NamespacedName{
+						Namespace: "envoy-gateway-system",
+						Name:      "envoy-gateway-lb",
+					}, "/metrics"); err != nil {
+						t.Logf("failed to get metric: %v", err)
+						return false, nil
+					}
+					return true, nil
+				}); err != nil {
+				t.Errorf("failed to scrape metrics: %v", err)
+			}
+		})
+	},
+}