Arnaud Mandy focused on stabilizing the compute_pressure_duplicate_updates test suite in the mozilla/gecko-dev repository, addressing persistent flakiness in continuous integration. By identifying and correcting a misplaced parenthesis in the JavaScript test code, Arnaud ensured that ownContributionEstimate was passed correctly, directly reducing unreliable test outcomes. He enhanced the suite by adding assertions to validate ownContributionEstimate values for both 'critical' and 'nominal' states, further preventing regression. Through consolidating duplicate update tests, Arnaud improved both coverage and maintainability. His work demonstrated strong debugging and JavaScript testing skills, resulting in a more robust validation process for performance-related changes in web platform testing.