test(alert): drain notifications before teardown

internal/alert/engine.go

@@ -61,9 +61,20 @@ type Engine struct {
 	stuckThresholds   map[string]time.Duration
 
 	closeOnce sync.Once
+	notifyWG  sync.WaitGroup
 	done      chan struct{}
 }
 
+func (e *Engine) dispatchNotification(ctx context.Context, payload notification.Payload) {
+	e.notifyWG.Add(1)
+	go func() {
+		defer e.notifyWG.Done()
+		e.hub.Dispatch(ctx, payload)
+	}()
+}
+
+func (e *Engine) waitNotifications() { e.notifyWG.Wait() }
+
 // NewEngine builds the engine. agentOfflineFloor + tickPeriod default
 // to 15min and 60s respectively when zero.
 func NewEngine(st *store.Store, hub *notification.Hub) *Engine {