Worked on the nextcloud/android repository to enhance the reliability and maintainability of the FilesSyncHelper component. Addressed a critical bug in file traversal by introducing null checks and safeguards against infinite recursion, ensuring robust handling of directory structures. Expanded unit test coverage using Java and Mockito, focusing on edge cases such as null handling during randomized file tree walks. Improved the readability and style of test code to support ongoing quality efforts. The work emphasized Android development best practices, bug fixing, and effective mocking strategies, directly contributing to the product’s stability and aligning with long-term goals for test quality and maintainability.