diff --git a/retrieval/discovery/marathon/marathon_test.go b/retrieval/discovery/marathon/marathon_test.go
index 6400baded..6ee398881 100644
--- a/retrieval/discovery/marathon/marathon_test.go
+++ b/retrieval/discovery/marathon/marathon_test.go
@@ -24,108 +24,114 @@ import (
 	"github.com/prometheus/prometheus/config"
 )
 
-var marathonValidLabel = map[string]string{"prometheus": "yes"}
+var (
+	marathonValidLabel = map[string]string{"prometheus": "yes"}
+	testServers        = []string{"http://localhost:8080"}
+)
 
-func newTestDiscovery(client AppListClient) (chan []*config.TargetGroup, *Discovery) {
-	ch := make(chan []*config.TargetGroup)
-	md := &Discovery{
-		Servers: []string{"http://localhost:8080"},
+func testUpdateServices(client AppListClient, ch chan []*config.TargetGroup) error {
+	md := Discovery{
+		Servers: testServers,
 		Client:  client,
 	}
-	return ch, md
+	return md.updateServices(context.Background(), ch)
 }
 
 func TestMarathonSDHandleError(t *testing.T) {
-	var errTesting = errors.New("testing failure")
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return nil, errTesting
-	})
-	go func() {
-		select {
-		case tg := <-ch:
-			t.Fatalf("Got group: %s", tg)
-		default:
-		}
-	}()
-	err := md.updateServices(context.Background(), ch)
-	if err != errTesting {
+	var (
+		errTesting = errors.New("testing failure")
+		ch         = make(chan []*config.TargetGroup, 1)
+		client     = func(url string) (*AppList, error) { return nil, errTesting }
+	)
+	if err := testUpdateServices(client, ch); err != errTesting {
 		t.Fatalf("Expected error: %s", err)
 	}
+	select {
+	case tg := <-ch:
+		t.Fatalf("Got group: %s", tg)
+	default:
+	}
 }
 
 func TestMarathonSDEmptyList(t *testing.T) {
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return &AppList{}, nil
-	})
-	go func() {
-		select {
-		case tg := <-ch:
-			if len(tg) > 0 {
-				t.Fatalf("Got group: %v", tg)
-			}
-		default:
-		}
-	}()
-	err := md.updateServices(context.Background(), ch)
-	if err != nil {
+	var (
+		ch     = make(chan []*config.TargetGroup, 1)
+		client = func(url string) (*AppList, error) { return &AppList{}, nil }
+	)
+	if err := testUpdateServices(client, ch); err != nil {
 		t.Fatalf("Got error: %s", err)
 	}
+	select {
+	case tg := <-ch:
+		if len(tg) > 0 {
+			t.Fatalf("Got group: %v", tg)
+		}
+	default:
+	}
 }
 
 func marathonTestAppList(labels map[string]string, runningTasks int) *AppList {
-	task := Task{
-		ID:    "test-task-1",
-		Host:  "mesos-slave1",
-		Ports: []uint32{31000},
-	}
-	docker := DockerContainer{Image: "repo/image:tag"}
-	container := Container{Docker: docker}
-	app := App{
-		ID:           "test-service",
-		Tasks:        []Task{task},
-		RunningTasks: runningTasks,
-		Labels:       labels,
-		Container:    container,
-	}
+	var (
+		task = Task{
+			ID:    "test-task-1",
+			Host:  "mesos-slave1",
+			Ports: []uint32{31000},
+		}
+		docker    = DockerContainer{Image: "repo/image:tag"}
+		container = Container{Docker: docker}
+		app       = App{
+			ID:           "test-service",
+			Tasks:        []Task{task},
+			RunningTasks: runningTasks,
+			Labels:       labels,
+			Container:    container,
+		}
+	)
 	return &AppList{
 		Apps: []App{app},
 	}
 }
 
 func TestMarathonSDSendGroup(t *testing.T) {
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return marathonTestAppList(marathonValidLabel, 1), nil
-	})
-	go func() {
-		select {
-		case tgs := <-ch:
-			tg := tgs[0]
-
-			if tg.Source != "test-service" {
-				t.Fatalf("Wrong target group name: %s", tg.Source)
-			}
-			if len(tg.Targets) != 1 {
-				t.Fatalf("Wrong number of targets: %v", tg.Targets)
-			}
-			tgt := tg.Targets[0]
-			if tgt[model.AddressLabel] != "mesos-slave1:31000" {
-				t.Fatalf("Wrong target address: %s", tgt[model.AddressLabel])
-			}
-		default:
-			t.Fatal("Did not get a target group.")
+	var (
+		ch     = make(chan []*config.TargetGroup, 1)
+		client = func(url string) (*AppList, error) {
+			return marathonTestAppList(marathonValidLabel, 1), nil
 		}
-	}()
-	err := md.updateServices(context.Background(), ch)
-	if err != nil {
+	)
+	if err := testUpdateServices(client, ch); err != nil {
 		t.Fatalf("Got error: %s", err)
 	}
+	select {
+	case tgs := <-ch:
+		tg := tgs[0]
+
+		if tg.Source != "test-service" {
+			t.Fatalf("Wrong target group name: %s", tg.Source)
+		}
+		if len(tg.Targets) != 1 {
+			t.Fatalf("Wrong number of targets: %v", tg.Targets)
+		}
+		tgt := tg.Targets[0]
+		if tgt[model.AddressLabel] != "mesos-slave1:31000" {
+			t.Fatalf("Wrong target address: %s", tgt[model.AddressLabel])
+		}
+	default:
+		t.Fatal("Did not get a target group.")
+	}
 }
 
 func TestMarathonSDRemoveApp(t *testing.T) {
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return marathonTestAppList(marathonValidLabel, 1), nil
-	})
-
+	var (
+		ch     = make(chan []*config.TargetGroup)
+		client = func(url string) (*AppList, error) {
+			return marathonTestAppList(marathonValidLabel, 1), nil
+		}
+		md = Discovery{
+			Servers: testServers,
+			Client:  client,
+		}
+	)
 	go func() {
 		up1 := (<-ch)[0]
 		up2 := (<-ch)[0]
@@ -151,73 +157,80 @@ func TestMarathonSDRemoveApp(t *testing.T) {
 }
 
 func TestMarathonSDRunAndStop(t *testing.T) {
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return marathonTestAppList(marathonValidLabel, 1), nil
-	})
-	md.RefreshInterval = time.Millisecond * 10
+	var (
+		ch     = make(chan []*config.TargetGroup)
+		client = func(url string) (*AppList, error) {
+			return marathonTestAppList(marathonValidLabel, 1), nil
+		}
+		md = Discovery{
+			Servers:         testServers,
+			Client:          client,
+			RefreshInterval: time.Millisecond * 10,
+		}
+	)
 	ctx, cancel := context.WithCancel(context.Background())
 
 	go func() {
-		select {
-		case <-ch:
-			cancel()
-		case <-time.After(md.RefreshInterval * 3):
-			cancel()
-			t.Fatalf("Update took too long.")
+		for {
+			select {
+			case _, ok := <-ch:
+				if !ok {
+					return
+				}
+				cancel()
+			case <-time.After(md.RefreshInterval * 3):
+				cancel()
+				t.Fatalf("Update took too long.")
+			}
 		}
 	}()
 
 	md.Run(ctx, ch)
-
-	select {
-	case <-ch:
-	default:
-		t.Fatalf("Channel not closed.")
-	}
 }
 
 func marathonTestZeroTaskPortAppList(labels map[string]string, runningTasks int) *AppList {
-	task := Task{
-		ID:    "test-task-2",
-		Host:  "mesos-slave-2",
-		Ports: []uint32{},
-	}
-	docker := DockerContainer{Image: "repo/image:tag"}
-	container := Container{Docker: docker}
-	app := App{
-		ID:           "test-service-zero-ports",
-		Tasks:        []Task{task},
-		RunningTasks: runningTasks,
-		Labels:       labels,
-		Container:    container,
-	}
+	var (
+		task = Task{
+			ID:    "test-task-2",
+			Host:  "mesos-slave-2",
+			Ports: []uint32{},
+		}
+		docker    = DockerContainer{Image: "repo/image:tag"}
+		container = Container{Docker: docker}
+		app       = App{
+			ID:           "test-service-zero-ports",
+			Tasks:        []Task{task},
+			RunningTasks: runningTasks,
+			Labels:       labels,
+			Container:    container,
+		}
+	)
 	return &AppList{
 		Apps: []App{app},
 	}
 }
 
 func TestMarathonZeroTaskPorts(t *testing.T) {
-	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
-		return marathonTestZeroTaskPortAppList(marathonValidLabel, 1), nil
-	})
-
-	go func() {
-		select {
-		case tgs := <-ch:
-			tg := tgs[0]
-
-			if tg.Source != "test-service-zero-ports" {
-				t.Fatalf("Wrong target group name: %s", tg.Source)
-			}
-			if len(tg.Targets) != 0 {
-				t.Fatalf("Wrong number of targets: %v", tg.Targets)
-			}
-		default:
-			t.Fatal("Did not get a target group.")
+	var (
+		ch     = make(chan []*config.TargetGroup, 1)
+		client = func(url string) (*AppList, error) {
+			return marathonTestZeroTaskPortAppList(marathonValidLabel, 1), nil
 		}
-	}()
-	err := md.updateServices(context.Background(), ch)
-	if err != nil {
+	)
+	if err := testUpdateServices(client, ch); err != nil {
 		t.Fatalf("Got error: %s", err)
 	}
+	select {
+	case tgs := <-ch:
+		tg := tgs[0]
+
+		if tg.Source != "test-service-zero-ports" {
+			t.Fatalf("Wrong target group name: %s", tg.Source)
+		}
+		if len(tg.Targets) != 0 {
+			t.Fatalf("Wrong number of targets: %v", tg.Targets)
+		}
+	default:
+		t.Fatal("Did not get a target group.")
+	}
 }