test: make the kube auth method test helper use freeport (#7788)

agent/consul/authmethod/kubeauth/testing.go

@@ -4,16 +4,21 @@ import (
 	"bytes"
 	"encoding/json"
 	"encoding/pem"
+	"fmt"
 	"io/ioutil"
+	"log"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"regexp"
+	"strconv"
 	"strings"
 	"sync"
-	"testing"
 	"time"
 
+	"github.com/hashicorp/consul/sdk/freeport"
+	"github.com/mitchellh/go-testing-interface"
 	"github.com/stretchr/testify/require"
 	authv1 "k8s.io/api/authentication/v1"
 	corev1 "k8s.io/api/core/v1"
@@ -28,9 +33,9 @@ import (
 //   - GET  /api/v1/namespaces/<NAMESPACE>/serviceaccounts/<NAME>
 //
 type TestAPIServer struct {
-	t      *testing.T
 	srv        *httptest.Server
 	caCert     string
+	returnFunc func()
 
 	mu                       sync.Mutex
 	authorizedJWT            string                 // token review and sa read
@@ -41,10 +46,16 @@ type TestAPIServer struct {
 
 // StartTestAPIServer creates a disposable TestAPIServer and binds it to a
 // random free port.
-func StartTestAPIServer(t *testing.T) *TestAPIServer {
-	s := &TestAPIServer{t: t}
+func StartTestAPIServer(t testing.T) *TestAPIServer {
+	s := &TestAPIServer{}
 
-	s.srv = httptest.NewTLSServer(s)
+	ports := freeport.MustTake(1)
+	s.returnFunc = func() {
+		freeport.Return(ports)
+	}
+	s.srv = httptestNewUnstartedServerWithPort(s, ports[0])
+	s.srv.Config.ErrorLog = log.New(ioutil.Discard, "", 0)
+	s.srv.StartTLS()
 
 	bs := s.srv.TLS.Certificates[0].Certificate[0]
 
@@ -90,6 +101,10 @@ func (s *TestAPIServer) SetAllowedServiceAccount(
 // Stop stops the running TestAPIServer.
 func (s *TestAPIServer) Stop() {
 	s.srv.Close()
+	if s.returnFunc != nil {
+		s.returnFunc()
+		s.returnFunc = nil
+	}
 }
 
 // Addr returns the current base URL for the running webserver.
@@ -530,3 +545,19 @@ func createStatus(status, message string, reason metav1.StatusReason, details *m
 		Code:     code,
 	}
 }
+
+func httptestNewUnstartedServerWithPort(handler http.Handler, port int) *httptest.Server {
+	if port == 0 {
+		return httptest.NewUnstartedServer(handler)
+	}
+	addr := net.JoinHostPort("127.0.0.1", strconv.Itoa(port))
+	l, err := net.Listen("tcp", addr)
+	if err != nil {
+		panic(fmt.Sprintf("httptest: failed to listen on a port: %v", err))
+	}
+
+	return &httptest.Server{
+		Listener: l,
+		Config:   &http.Server{Handler: handler},
+	}
+}