The blog post by Gleb Bahmutov explores how to test edge data cases in web applications using network stubbing and app actions with Cypress, focusing on scenarios where historical data might include incomplete entries that current UI validations prevent. Using a TodoMVC application as a case study, it demonstrates how to test for edge cases like blank titles, which the application now disallows through stricter input validation. The post explains how to use Cypress to simulate and intercept network requests, allowing developers to test how applications handle data that cannot be created via the current UI. By leveraging Cypress's network stubbing and the capability to directly manipulate the application state with App Actions, developers can ensure that their applications handle unexpected data gracefully without UI-induced errors. The article concludes by highlighting that while the application prevents new blank entries, it can still display existing ones without crashing, albeit imperfectly, thereby maintaining robustness against legacy data issues.