you may build some mock / simulator which substitute your backend services , and by that control the expected data your streaming to the client.
Then build some UI view Model , and each time the price change in UI update your view model , with custom comparator you can compare your view models (page classes) …
I’m running a mobile automation team @Citi bank , we are doing many cool stuff in fintec area for both , Android / iOS platforms , myself or any other team member will be happy to help if needed
GoodLuck