Fix flaky test embed.TestEnableAuth which can fail due to port conflict

server/embed/auth_test.go

@@ -17,12 +17,19 @@ package embed
 import (
 	"testing"
 
+	"go.etcd.io/etcd/server/v3/embed/testutil"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/v3client"
 )
 
 func TestEnableAuth(t *testing.T) {
 	tdir := t.TempDir()
 	cfg := NewConfig()
+
+	testURLConfig := testutil.NewConfigTestURLs()
+	cfg.ListenClientUrls, cfg.AdvertiseClientUrls = testURLConfig.ClientURLs, testURLConfig.ClientURLs
+	cfg.ListenPeerUrls, cfg.AdvertisePeerUrls = testURLConfig.PeerURLs, testURLConfig.PeerURLs
+	cfg.InitialCluster = testURLConfig.InitialCluster
+
 	cfg.Dir = tdir
 	e, err := StartEtcd(cfg)
 	if err != nil {

server/embed/serve_test.go

@@ -15,14 +15,12 @@
 package embed
 
 import (
-	"fmt"
-	"net/url"
-	"os"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"go.etcd.io/etcd/server/v3/auth"
+	"go.etcd.io/etcd/server/v3/embed/testutil"
 )
 
 // TestStartEtcdWrongToken ensures that StartEtcd with wrong configs returns with error.
@@ -31,29 +29,14 @@ func TestStartEtcdWrongToken(t *testing.T) {
 
 	cfg := NewConfig()
 
-	// Similar to function in integration/embed/embed_test.go for setting up Config.
-	urls := newEmbedURLs(2)
-	curls := []url.URL{urls[0]}
-	purls := []url.URL{urls[1]}
-	cfg.ListenClientUrls, cfg.AdvertiseClientUrls = curls, curls
-	cfg.ListenPeerUrls, cfg.AdvertisePeerUrls = purls, purls
-	cfg.InitialCluster = ""
-	for i := range purls {
-		cfg.InitialCluster += ",default=" + purls[i].String()
-	}
-	cfg.InitialCluster = cfg.InitialCluster[1:]
+	testURLConfig := testutil.NewConfigTestURLs()
+	cfg.ListenClientUrls, cfg.AdvertiseClientUrls = testURLConfig.ClientURLs, testURLConfig.ClientURLs
+	cfg.ListenPeerUrls, cfg.AdvertisePeerUrls = testURLConfig.PeerURLs, testURLConfig.PeerURLs
+	cfg.InitialCluster = testURLConfig.InitialCluster
+
 	cfg.Dir = tdir
 	cfg.AuthToken = "wrong-token"
 
 	_, err := StartEtcd(cfg)
 	require.ErrorIsf(t, err, auth.ErrInvalidAuthOpts, "expected %v, got %v", auth.ErrInvalidAuthOpts, err)
 }
-
-func newEmbedURLs(n int) (urls []url.URL) {
-	scheme := "unix"
-	for i := 0; i < n; i++ {
-		u, _ := url.Parse(fmt.Sprintf("%s://localhost:%d%06d", scheme, os.Getpid(), i))
-		urls = append(urls, *u)
-	}
-	return urls
-}

server/embed/testutil/url.go

@@ -0,0 +1,51 @@
+// Copyright 2026 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testutil
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+)
+
+type ConfigTestURLs struct {
+	PeerURLs       []url.URL
+	ClientURLs     []url.URL
+	InitialCluster string
+}
+
+// Similar to function in integration/embed/embed_test.go for setting up Config.
+func NewConfigTestURLs() *ConfigTestURLs {
+	urls := newEmbedURLs(2)
+	cfg := &ConfigTestURLs{
+		ClientURLs:     []url.URL{urls[0]},
+		PeerURLs:       []url.URL{urls[1]},
+		InitialCluster: "",
+	}
+	for i := range cfg.PeerURLs {
+		cfg.InitialCluster += ",default=" + cfg.PeerURLs[i].String()
+	}
+	cfg.InitialCluster = cfg.InitialCluster[1:]
+	return cfg
+}
+
+func newEmbedURLs(n int) (urls []url.URL) {
+	scheme := "unix"
+	for i := 0; i < n; i++ {
+		u, _ := url.Parse(fmt.Sprintf("%s://localhost:%d%06d", scheme, os.Getpid(), i))
+		urls = append(urls, *u)
+	}
+	return urls
+}