From 16db8e2375fa2019ffbabb76a261cebb92e7b287 Mon Sep 17 00:00:00 2001
From: yongruilin <yongrlin@outlook.com>
Date: Fri, 31 Oct 2025 05:21:40 +0000
Subject: [PATCH] feat: add integration test for /flagz kube-apiserver endpoint

---
 .../controlplane/kube_apiserver_test.go       | 127 ++++++++++++++----
 1 file changed, 101 insertions(+), 26 deletions(-)

diff --git a/test/integration/controlplane/kube_apiserver_test.go b/test/integration/controlplane/kube_apiserver_test.go
index e9d684e2c5d..ff633c65e9c 100644
--- a/test/integration/controlplane/kube_apiserver_test.go
+++ b/test/integration/controlplane/kube_apiserver_test.go
@@ -49,6 +49,7 @@ import (
 	"k8s.io/kubernetes/test/integration/etcd"
 	"k8s.io/kubernetes/test/integration/framework"
 
+	flagzv1alpha1 "k8s.io/apiserver/pkg/server/flagz/api/v1alpha1"
 	v1alpha1 "k8s.io/apiserver/pkg/server/statusz/api/v1alpha1"
 )
 
@@ -135,7 +136,7 @@ func TestLivezAndReadyz(t *testing.T) {
 
 func TestFlagz(t *testing.T) {
 	featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.ComponentFlagz, true)
-	testServerFlags := append(framework.DefaultTestServerFlags(), "--emulated-version=1.32")
+	testServerFlags := append(framework.DefaultTestServerFlags(), "--v=2")
 	server := kubeapiservertesting.StartTestServerOrDie(t, nil, testServerFlags, framework.SharedEtcd())
 	defer server.TearDownFn()
 
@@ -144,33 +145,107 @@ func TestFlagz(t *testing.T) {
 		t.Fatalf("Unexpected error: %v", err)
 	}
 
-	res := client.CoreV1().RESTClient().Get().RequestURI("/flagz").Do(context.TODO())
-	var status int
-	res.StatusCode(&status)
-	if status != http.StatusOK {
-		t.Fatalf("flagz/ should be healthy, got %v", status)
+	wantBodyStr := "kube-apiserver flagz\nWarning: This endpoint is not meant to be machine parseable"
+	wantBodyJSON := &flagzv1alpha1.Flagz{
+		TypeMeta: metav1.TypeMeta{
+			Kind:       "Flagz",
+			APIVersion: "config.k8s.io/v1alpha1",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "kube-apiserver",
+		},
 	}
 
-	expectedHeader := `
-kube-apiserver flags
-Warning: This endpoint is not meant to be machine parseable, has no formatting compatibility guarantees and is for debugging purposes only.`
-
-	raw, err := res.Raw()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !bytes.HasPrefix(raw, []byte(expectedHeader)) {
-		t.Fatalf("Header mismatch!\nExpected:\n%s\n\nGot:\n%s", expectedHeader, string(raw))
-	}
-	found := false
-	for _, line := range strings.Split(string(raw), "\n") {
-		if strings.Contains(line, "emulated-version") && strings.Contains(line, "1.32") {
-			found = true
-			break
-		}
-	}
-	if !found {
-		t.Fatalf("Expected flag --emulated-version=[1.32] to be reflected in /flagz output, got:\n%s", string(raw))
+	for _, tc := range []struct {
+		name         string
+		acceptHeader string
+		wantStatus   int
+		wantBodySub  string               // for text/plain
+		wantJSON     *flagzv1alpha1.Flagz // for application/json
+	}{
+		{
+			name:         "text plain response",
+			acceptHeader: "text/plain",
+			wantStatus:   http.StatusOK,
+			wantBodySub:  wantBodyStr,
+		},
+		{
+			name:         "structured json response",
+			acceptHeader: "application/json;v=v1alpha1;g=config.k8s.io;as=Flagz",
+			wantStatus:   http.StatusOK,
+			wantJSON:     wantBodyJSON,
+		},
+		{
+			name:         "no accept header (defaults to text)",
+			acceptHeader: "",
+			wantStatus:   http.StatusOK,
+			wantBodySub:  wantBodyStr,
+		},
+		{
+			name:         "invalid accept header",
+			acceptHeader: "application/xml",
+			wantStatus:   http.StatusNotAcceptable,
+		},
+		{
+			name:         "application/json without params",
+			acceptHeader: "application/json",
+			wantStatus:   http.StatusNotAcceptable,
+		},
+		{
+			name:         "application/json with missing as",
+			acceptHeader: "application/json;v=v1alpha1;g=config.k8s.io",
+			wantStatus:   http.StatusNotAcceptable,
+		},
+		{
+			name:         "wildcard accept header",
+			acceptHeader: "*/*",
+			wantStatus:   http.StatusOK,
+			wantBodySub:  wantBodyStr,
+		},
+		{
+			name:         "bad json header fall back wildcard",
+			acceptHeader: "application/json;v=foo;g=config.k8s.io;as=Flagz,*/*",
+			wantStatus:   http.StatusOK,
+			wantBodySub:  wantBodyStr,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			req := client.CoreV1().RESTClient().Get().RequestURI("/flagz")
+			req.SetHeader("Accept", tc.acceptHeader)
+			res := req.Do(context.TODO())
+			var status int
+			res.StatusCode(&status)
+			if status != tc.wantStatus {
+				t.Fatalf("want status %d, got %d", tc.wantStatus, status)
+			}
+			raw, err := res.Raw()
+			if err != nil && tc.wantStatus == http.StatusOK {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if tc.wantStatus == http.StatusOK {
+				if tc.wantBodySub != "" {
+					if !bytes.Contains(raw, []byte(tc.wantBodySub)) {
+						t.Errorf("body missing expected substring: %q\nGot:\n%s", tc.wantBodySub, string(raw))
+					}
+				}
+				if tc.wantJSON != nil {
+					var got flagzv1alpha1.Flagz
+					if err := json.Unmarshal(raw, &got); err != nil {
+						t.Fatalf("error unmarshalling JSON: %v", err)
+					}
+					// Only check static fields, since others are dynamic
+					if got.TypeMeta != tc.wantJSON.TypeMeta {
+						t.Errorf("TypeMeta mismatch: want %+v, got %+v", tc.wantJSON.TypeMeta, got.TypeMeta)
+					}
+					if got.ObjectMeta.Name != tc.wantJSON.ObjectMeta.Name {
+						t.Errorf("ObjectMeta.Name mismatch: want %q, got %q", tc.wantJSON.ObjectMeta.Name, got.ObjectMeta.Name)
+					}
+					if got.Flags["v"] != "2" {
+						t.Errorf("v mismatch: want %q, got %q", "2", got.Flags["v"])
+					}
+				}
+			}
+		})
 	}
 }