feat(pubsub/pstest): add support to register other servers into grpc.Server

pubsub/pstest/fake.go

@@ -37,6 +37,7 @@ import (
 	"cloud.google.com/go/internal/testutil"
 	pb "cloud.google.com/go/pubsub/apiv1/pubsubpb"
 	"go.einride.tech/aip/filtering"
+	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 	durpb "google.golang.org/protobuf/types/known/durationpb"
@@ -111,6 +112,13 @@ func NewServer(opts ...ServerReactorOption) *Server {
 
 // NewServerWithPort creates a new fake server running in the current process at the specified port.
 func NewServerWithPort(port int, opts ...ServerReactorOption) *Server {
+	return NewServerWithCallback(port, func(*grpc.Server) { /* empty */ }, opts...)
+}
+
+// NewServerWithCallback creates new fake server running in the current process at the specified port.
+// Before starting the server, the provided callback is called to allow caller to register additional fakes
+// into grpc server.
+func NewServerWithCallback(port int, callback func(*grpc.Server), opts ...ServerReactorOption) *Server {
 	srv, err := testutil.NewServerWithPort(port)
 	if err != nil {
 		panic(fmt.Sprintf("pstest.NewServerWithPort: %v", err))
@@ -136,6 +144,9 @@ func NewServerWithPort(port int, opts ...ServerReactorOption) *Server {
 	pb.RegisterPublisherServer(srv.Gsrv, &s.GServer)
 	pb.RegisterSubscriberServer(srv.Gsrv, &s.GServer)
 	pb.RegisterSchemaServiceServer(srv.Gsrv, &s.GServer)
+
+	callback(srv.Gsrv)
+
 	srv.Start()
 	return s
 }

pubsub/pstest/fake_test.go

@@ -27,10 +27,12 @@ import (
 	"testing"
 	"time"
 
+	iampb "cloud.google.com/go/iam/apiv1/iampb"
 	"cloud.google.com/go/internal/testutil"
 	pb "cloud.google.com/go/pubsub/apiv1/pubsubpb"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/status"
 	"google.golang.org/protobuf/types/known/durationpb"
 	field_mask "google.golang.org/protobuf/types/known/fieldmaskpb"
@@ -62,6 +64,47 @@ func TestNewServerWithPort(t *testing.T) {
 	defer conn.Close()
 }
 
+func TestNewServerWithCallback(t *testing.T) {
+	// Allocate an available port to use with NewServerWithPort and then close it so it's available.
+	// Note: There is no guarantee that the port does not become used between closing
+	// the listener and creating the new server with NewServerWithPort, but the chances are
+	// very small.
+	l, err := net.Listen("tcp", ":0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	port := l.Addr().(*net.TCPAddr).Port
+	l.Close()
+
+	additionalFake := struct {
+		iampb.UnimplementedIAMPolicyServer
+	}{}
+
+	verifyCallback := false
+	callback := func(grpc *grpc.Server) {
+		// register something
+		iampb.RegisterIAMPolicyServer(grpc, &additionalFake)
+		verifyCallback = true
+	}
+
+	// Pass a non 0 port to demonstrate we can pass a hardcoded port for the server to listen on
+	srv := NewServerWithCallback(port, callback)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer srv.Close()
+
+	conn, err := grpc.NewClient(srv.Addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	if !verifyCallback {
+		t.Fatal("callback was not invoked")
+	}
+}
+
 func TestTopics(t *testing.T) {
 	pclient, sclient, server, cleanup := newFake(context.TODO(), t)
 	defer cleanup()