Uber Migrates 75,000+ Test Classes from Junit 4 to Junit 5 Using Automated Code Transformation (opens in new tab)

Uber engineers migrated over 75,000 test classes from JUnit 4 to JUnit 5 using automated code transformation with OpenRewrite and internal orchestration. By enabling the JUnit Platform for dual execution with Bazel and validating changes through CI, the team modernized testing infrastructure while maintaining correctness at monorepo scale. By Leela Kumili