Worked on the firebase/firebase-ios-sdk repository to deliver a comprehensive integration test suite for phone number authentication in the iOS SDK. Focused on both callback-based and async/await sign-in flows, the work enhanced end-to-end test coverage and improved the reliability of SMS-based authentication. Leveraged Swift to implement integration and unit testing, ensuring that critical authentication paths are robust against regressions. The new tests strengthened the CI feedback loop, enabling faster detection of issues in authentication workflows. This contribution improved release readiness for the SDK and provided greater confidence for customers relying on Firebase Authentication in their iOS applications.