add method to check if notification is scheduled (for testing

src/services/NotificationService.ts

@@ -91,6 +91,15 @@ export class NotificationService {
 
   }
 
+  /**
+   * Check whether the notification is scheduled.
+   * @param deviceId
+   * @param shuttleId
+   * @param stopId
+   */
+  public isNotificationScheduled({ deviceId, shuttleId, stopId }: ScheduledNotificationData) {
+  }
+
   public cancelAllNotifications(deviceId: string) {
 
   }