Oliver Davies recounts a recent experience with a Drupal project featuring multiple custom modules, where the removal of an unused method inadvertently disrupted cron job functionality. Despite passing tests and successful deployment of the change, the absence of architectural boundaries led to unexpected errors. This incident prompted Oliver to explore architectural testing as a means to enforce module-specific code usage and establish clearer layering within each module. By implementing such measures, future issues could be identified and addressed proactively, minimizing the risk of production disruptions.