Detox is another great tool I wish I had earlier. What Detox does is best described in their documentation:
High velocity native mobile development requires us to adopt continuous integration workflows, which means our reliance on manual QA has to drop significantly. Detox tests your mobile app while it's running in a real device/simulator, interacting with it just like a real user.
Getting started with Detox in React Native is fairly straight forward. You can find their Introduction here.