Worked on the slackapi/java-slack-sdk repository to enhance the reliability of usergroup management by addressing a bug in the usergroups.users.update endpoint. Improved the API’s robustness by ensuring that when an empty user list is provided, the system sends a valid empty array instead of a null value, thereby preventing update errors. This change involved updating Java code and expanding unit tests to cover empty-list scenarios, reducing the risk of regressions. Focused on API development and unit testing, the work improved data handling and overall stability for Slack API integrations, contributing to higher code quality and more predictable usergroup management behavior.