Xu contributed to the apache/spark repository by enhancing test infrastructure and data reliability within Spark SQL and the JDBC client. Over two months, Xu focused on aligning test suite paths with package structures, improving test organization and reducing CI failures using Scala and software engineering best practices. Xu also developed targeted unit and integration tests for the JDBC path, specifically validating UTF-8 decoding of BINARY columns to prevent encoding regressions in production data pipelines. These efforts did not introduce user-facing changes but strengthened the reliability and maintainability of Spark’s testing framework, demonstrating depth in testing and data correctness using Scala and Spark.