A Developer's Guide to Testing Beyond Happy-Path Checks

The article argues that software testing should go beyond confirming correct return values, since real failures like unavailable backends or interrupted operations also matter. It describes unit tests as isolated checks of functions, classes, or methods, covering valid and invalid inputs, boundary values, and dependency failures. Mocking and stubbing are presented as ways to isolate dependencies such as databases. Component tests are described as covering larger parts of an application, such as a UI screen or API service, including loading states, error messages, and stale responses. Integration tests then check whether connected components, such as a service and database or a UI and backend, work together correctly.