The company Pillow, which is backed by some of the best investors in Silicon Valley, uses unit tests and end-to-end tests to ensure high product quality for its mobile app. The team releases updates every 2 weeks and uses Jest for unit tests and Detox for end-to-end tests. They also use Bitrise as a CI service to automate their testing process. The tests cover various aspects of the app, including redux actions, reducers, and UI components. The team uses snapshot testing with Jest to ensure that the UI does not change unexpectedly. They have found that using unit and end-to-end tests has given them the freedom to make substantial changes to the app without worrying about breaking existing functionality.