@@ -66,24 +66,27 @@ type ServiceSpecOpt func(*swarmtypes.ServiceSpec)

 // CreateService creates a service on the passed in swarm daemon.

 func CreateService(t *testing.T, d *daemon.Daemon, opts ...ServiceSpecOpt) string {

 	t.Helper()

-	spec := defaultServiceSpec()

-	for _, o := range opts {

-		o(&spec)

-	}

 	client := d.NewClientT(t)

 	defer client.Close()

+	spec := CreateServiceSpec(t, opts...)

 	resp, err := client.ServiceCreate(context.Background(), spec, types.ServiceCreateOptions{})

 	assert.NilError(t, err, "error creating service")

 	return resp.ID

 }

-func defaultServiceSpec() swarmtypes.ServiceSpec {

+// CreateServiceSpec creates a default service-spec, and applies the provided options

+func CreateServiceSpec(t *testing.T, opts ...ServiceSpecOpt) swarmtypes.ServiceSpec {

+	t.Helper()

 	var spec swarmtypes.ServiceSpec

 	ServiceWithImage("busybox:latest")(&spec)

 	ServiceWithCommand([]string{"/bin/top"})(&spec)

 	ServiceWithReplicas(1)(&spec)

+

+	for _, o := range opts {

+		o(&spec)

+	}

 	return spec

 }

@@ -4,6 +4,7 @@ import (

 	"context"

 	"fmt"

 	"io/ioutil"

+	"net/http"

 	"testing"

 	"time"

@@ -15,6 +16,7 @@ import (

 	"github.com/docker/docker/integration/internal/network"

 	"github.com/docker/docker/integration/internal/swarm"

 	"github.com/docker/docker/internal/test/daemon"

+	"github.com/docker/docker/internal/test/request"

 	"gotest.tools/assert"

 	is "gotest.tools/assert/cmp"

 	"gotest.tools/poll"

@@ -123,6 +125,34 @@ func TestCreateServiceMultipleTimes(t *testing.T) {

 	poll.WaitOn(t, networkIsRemoved(client, overlayID), poll.WithTimeout(1*time.Minute), poll.WithDelay(10*time.Second))

 }

+func TestCreateServiceConflict(t *testing.T) {

+	skip.If(t, testEnv.DaemonInfo.OSType == "windows")

+	defer setupTest(t)()

+	d := swarm.NewSwarm(t, testEnv)

+	defer d.Stop(t)

+

+	serviceName := "TestService_" + t.Name()

+	serviceSpec := []swarm.ServiceSpecOpt{

+		swarm.ServiceWithName(serviceName),

+	}

+

+	swarm.CreateService(t, d, serviceSpec...)

+

+	spec := swarm.CreateServiceSpec(t, serviceSpec...)

+	res, body, err := request.Post(

+		"/services/create",

+		request.Host(d.Sock()),

+		request.JSONBody(spec),

+		request.JSON,

+	)

+	assert.NilError(t, err)

+	assert.Equal(t, res.StatusCode, http.StatusConflict)

+

+	buf, err := request.ReadBody(body)

+	assert.NilError(t, err)

+	assert.Check(t, is.Contains(string(buf), "service "+serviceName+" already exists"))

+}

+

 func TestCreateWithDuplicateNetworkNames(t *testing.T) {

 	skip.If(t, testEnv.DaemonInfo.OSType == "windows")

 	defer setupTest(t)()