diff --git a/notifier/notifier.go b/notifier/notifier.go
index b3df6b177..5cee01eac 100644
--- a/notifier/notifier.go
+++ b/notifier/notifier.go
@@ -331,7 +331,7 @@ func (n *Notifier) sendAll(alerts ...*model.Alert) bool {
 			go func(am alertmanager) {
 				u := am.url()
 
-				if err := am.send(ctx, ams.client, b); err != nil {
+				if err := n.sendOne(ctx, ams.client, u, b); err != nil {
 					log.With("alertmanager", u).With("count", len(alerts)).Errorf("Error sending alerts: %s", err)
 					n.errors.WithLabelValues(u).Inc()
 				} else {
@@ -350,6 +350,20 @@ func (n *Notifier) sendAll(alerts ...*model.Alert) bool {
 	return numSuccess > 0
 }
 
+func (n *Notifier) sendOne(ctx context.Context, c *http.Client, url string, b []byte) error {
+	resp, err := ctxhttp.Post(ctx, c, url, contentTypeJSON, bytes.NewReader(b))
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	// Any HTTP status 2xx is OK.
+	if resp.StatusCode/100 != 2 {
+		return fmt.Errorf("bad response status %v", resp.Status)
+	}
+	return err
+}
+
 // Stop shuts down the notification handler.
 func (n *Notifier) Stop() {
 	log.Info("Stopping notification handler...")
@@ -381,39 +395,23 @@ func (n *Notifier) Collect(ch chan<- prometheus.Metric) {
 }
 
 // alertmanager holds Alertmanager endpoint information.
-type alertmanager struct {
-	plainURL string // test injection hook
-	labels   model.LabelSet
+type alertmanager interface {
+	url() string
 }
 
+type alertmanagerLabels model.LabelSet
+
 const pathLabel = "__alerts_path__"
 
-func (a alertmanager) url() string {
-	if a.plainURL != "" {
-		return a.plainURL
-	}
+func (a alertmanagerLabels) url() string {
 	u := &url.URL{
-		Scheme: string(a.labels[model.SchemeLabel]),
-		Host:   string(a.labels[model.AddressLabel]),
-		Path:   string(a.labels[pathLabel]),
+		Scheme: string(a[model.SchemeLabel]),
+		Host:   string(a[model.AddressLabel]),
+		Path:   string(a[pathLabel]),
 	}
 	return u.String()
 }
 
-func (a alertmanager) send(ctx context.Context, c *http.Client, b []byte) error {
-	resp, err := ctxhttp.Post(ctx, c, a.url(), contentTypeJSON, bytes.NewReader(b))
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
-
-	// Any HTTP status 2xx is OK.
-	if resp.StatusCode/100 != 2 {
-		return fmt.Errorf("bad response status %v", resp.Status)
-	}
-	return err
-}
-
 // alertmanagerSet contains a set of Alertmanagers discovered via a group of service
 // discovery definitions that have a common configuration on how alerts should be sent.
 type alertmanagerSet struct {
@@ -532,7 +530,7 @@ func alertmanagerFromGroup(tg *config.TargetGroup, cfg *config.AlertmanagerConfi
 			}
 		}
 
-		res = append(res, alertmanager{labels: lset})
+		res = append(res, alertmanagerLabels(lset))
 	}
 	return res, nil
 }
diff --git a/notifier/notifier_test.go b/notifier/notifier_test.go
index fdc86de53..65c49a3fa 100644
--- a/notifier/notifier_test.go
+++ b/notifier/notifier_test.go
@@ -23,7 +23,6 @@ import (
 	"time"
 
 	"github.com/prometheus/common/model"
-
 	"github.com/prometheus/prometheus/config"
 )
 
@@ -150,8 +149,12 @@ func TestHandlerSendAll(t *testing.T) {
 	h := New(&Options{})
 	h.alertmanagers = append(h.alertmanagers, &alertmanagerSet{
 		ams: []alertmanager{
-			{plainURL: server1.URL},
-			{plainURL: server2.URL},
+			alertmanagerMock{
+				urlf: func() string { return server1.URL },
+			},
+			alertmanagerMock{
+				urlf: func() string { return server2.URL },
+			},
 		},
 		cfg: &config.AlertmanagerConfig{
 			Timeout: time.Second,
@@ -312,7 +315,9 @@ func TestHandlerQueueing(t *testing.T) {
 	})
 	h.alertmanagers = append(h.alertmanagers, &alertmanagerSet{
 		ams: []alertmanager{
-			{plainURL: server.URL},
+			alertmanagerMock{
+				urlf: func() string { return server.URL },
+			},
 		},
 		cfg: &config.AlertmanagerConfig{
 			Timeout: time.Second,
@@ -371,3 +376,11 @@ func TestHandlerQueueing(t *testing.T) {
 		}
 	}
 }
+
+type alertmanagerMock struct {
+	urlf func() string
+}
+
+func (a alertmanagerMock) url() string {
+	return a.urlf()
+}