During October 2023, Tarjei contributed to the symfony/symfony repository by developing a configurable Mock Response Factory for the Symfony HttpClient component. This feature enables per-scope mock responses, allowing developers to define targeted mock behaviors for different scoped HTTP clients and resulting in more deterministic and reliable tests. Tarjei’s work focused on enhancing testability and reducing flakiness in scenarios involving scoped clients, addressing a common challenge in API development. The implementation leveraged PHP and Symfony, drawing on back end development expertise to improve the testing infrastructure. The contribution demonstrated thoughtful engineering depth within a focused, high-impact area of the codebase.