expand testing section with e2e info

Author: jaworek

src/docs/guides/testing.md

@@ -165,9 +165,17 @@ For large applications, prioritize tests by user impact:
 
 Don't aim for 100% code coverage. Focus on meaningful coverage of user-facing functionality.
 
+## End-to-End Testing
+
+For full end-to-end testing of your app running on Meta Horizon OS, you can use [Maestro](https://maestro.dev/) — an open-source UI testing framework that supports React Native apps. With the Meta Spatial Simulator, Maestro can automate user flows by interacting with your app just like a real user would: tapping elements, entering text, and validating screen content.
+
+[Maestro Studio](https://docs.maestro.dev/getting-started/maestro-studio-desktop) provides a visual IDE for building tests without writing code, while the CLI integrates seamlessly into CI pipelines. Since the testing workflow is standard across all React Native platforms, refer to the official Maestro documentation for setup and usage instructions.
+
 ## Further Reading
 
 - [React Native Testing Library Documentation](https://callstack.github.io/react-native-testing-library/)
 - [How to Query - RNTL Guide](https://callstack.github.io/react-native-testing-library/docs/guides/how-to-query)
 - [How to Know What to Test - Kent C. Dodds](https://kentcdodds.com/blog/how-to-know-what-to-test)
 - [Testing Implementation Details - Kent C. Dodds](https://kentcdodds.com/blog/testing-implementation-details)
+- [Maestro Documentation](https://docs.maestro.dev/)
+- [Maestro React Native Support](https://docs.maestro.dev/platform-support/react-native-support)