diff --git a/dispatch/dispatch_test.go b/dispatch/dispatch_test.go
index 46518686..db1f845c 100644
--- a/dispatch/dispatch_test.go
+++ b/dispatch/dispatch_test.go
@@ -335,40 +335,41 @@ func TestGroups(t *testing.T) {
 		t.Fatal(err)
 	}
 	route := NewRoute(conf.Route, nil)
-	marker := types.NewMarker(prometheus.DefaultRegisterer)
+	marker := types.NewMarker(prometheus.NewRegistry())
 	alerts, err := mem.NewAlerts(context.Background(), marker, time.Hour, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer alerts.Close()
 	timeout := func(d time.Duration) time.Duration { return time.Duration(0) }
-	dispatcher := NewDispatcher(alerts, route, &noopStage{}, marker, timeout, logger)
+	recorder := &recordStage{t: t, alerts: make(map[string]map[model.Fingerprint]*types.Alert)}
+	dispatcher := NewDispatcher(alerts, route, recorder, marker, timeout, logger)
 	go dispatcher.Run()
+	defer dispatcher.Stop()
 
-	// create alerts. the dispatcher will automatically create the groups
+	// Create alerts. the dispatcher will automatically create the groups.
 	alerts.Put(
 		newAlert(model.LabelSet{"env": "testing", "alertname": "TestingAlert", "service": "api"}),
 		newAlert(model.LabelSet{"env": "prod", "alertname": "HighErrorRate", "cluster": "aa", "service": "api"}),
 		newAlert(model.LabelSet{"env": "prod", "alertname": "HighErrorRate", "cluster": "bb", "service": "api"}),
 		newAlert(model.LabelSet{"env": "prod", "alertname": "HighLatency", "cluster": "bb", "service": "db", "kafka": "yes"}),
 	)
-	// Let alerts get processed
-	time.Sleep(time.Second)
 
-	var routeFilter, alertFilter bool
-	alertGroups, receivers := dispatcher.Groups(func(_ *Route) bool {
-		routeFilter = true
-		return true
-	}, func(_ *types.Alert, _ time.Time) bool {
-		alertFilter = true
-		return true
-	})
+	// Let alerts get processed.
+	for i := 0; len(recorder.Alerts()) != 5 && i < 10; i++ {
+		time.Sleep(100 * time.Millisecond)
+	}
+	require.Equal(t, 5, len(recorder.Alerts()))
 
-	// Verify filter functions were called
-	require.True(t, routeFilter)
-	require.True(t, alertFilter)
+	alertGroups, receivers := dispatcher.Groups(
+		func(*Route) bool {
+			return true
+		}, func(*types.Alert, time.Time) bool {
+			return true
+		},
+	)
 
-	// Verify grouping works
+	// Verify that grouping works.
 	require.Equal(t, 5, len(alertGroups))
 	for _, ag := range alertGroups {
 		if len(ag.Labels) == 2 {
@@ -387,9 +388,10 @@ func TestGroups(t *testing.T) {
 		for _, alert := range ag.Alerts {
 			alertsReceivers, ok := receivers[alert.Fingerprint()]
 			require.True(t, ok)
+			sort.Strings(alertsReceivers)
 			if labelValue := ag.Labels["alertname"]; string(labelValue) == "HighLatency" {
 				// Matches both prod and kafka receivers
-				require.Equal(t, []string{"prod", "kafka"}, alertsReceivers)
+				require.Equal(t, []string{"kafka", "prod"}, alertsReceivers)
 				continue
 			}
 			require.Equal(t, 1, len(alertsReceivers))
@@ -398,15 +400,45 @@ func TestGroups(t *testing.T) {
 	}
 }
 
-type noopStage struct{}
+type recordStage struct {
+	t      *testing.T
+	mtx    sync.RWMutex
+	alerts map[string]map[model.Fingerprint]*types.Alert
+}
 
-func (n *noopStage) Exec(ctx context.Context, l log.Logger, alerts ...*types.Alert) (context.Context, []*types.Alert, error) {
+func (r *recordStage) Alerts() []*types.Alert {
+	r.mtx.RLock()
+	defer r.mtx.RUnlock()
+	alerts := make([]*types.Alert, 0)
+	for k := range r.alerts {
+		for _, a := range r.alerts[k] {
+			alerts = append(alerts, a)
+		}
+	}
+	return alerts
+}
+
+func (r *recordStage) Exec(ctx context.Context, l log.Logger, alerts ...*types.Alert) (context.Context, []*types.Alert, error) {
+	r.mtx.Lock()
+	defer r.mtx.Unlock()
+	gk, ok := notify.GroupKey(ctx)
+	if !ok {
+		panic("GroupKey not present!")
+	}
+	if _, ok := r.alerts[gk]; !ok {
+		r.alerts[gk] = make(map[model.Fingerprint]*types.Alert)
+	}
+	for _, a := range alerts {
+		r.alerts[gk][a.Fingerprint()] = a
+	}
 	return ctx, nil, nil
 }
 
 var (
-	t0 = time.Now()
-	t1 = t0.Add(100 * time.Millisecond)
+	// Set the start time in the past to trigger a flush immediately.
+	t0 = time.Now().Add(-time.Minute)
+	// Set the end time in the future to avoid deleting the alert.
+	t1 = t0.Add(2 * time.Minute)
 )
 
 func newAlert(labels model.LabelSet) *types.Alert {