Achille Roussel developed custom storage support for the PromQL Test Suite in the grafana/prometheus repository, focusing on enhancing test flexibility and coverage. By modifying test functions to accept a storage parameter, Achille enabled the suite to run tests against different storage implementations, allowing for more targeted and storage-specific testing scenarios. This approach required updates to the test harness and careful integration with Go’s type system to ensure compatibility and maintainability. The work demonstrated a solid understanding of Go, software development best practices, and testing methodologies, delivering a focused feature that deepens the test suite’s adaptability without introducing unnecessary complexity.