What is the purpose of a stub in testing?

The purpose of a stub in testing is to replace an incomplete component that is invoked during a test. Stubs are generally used in integration testing when some parts of the system may not yet be available or fully developed. By providing a stub, testers can simulate the behavior of a missing component, allowing them to continue testing the interactions of other parts of the application. This enables the testing process to move forward without delay, ensuring that the relationships and interfaces between components can still be validated.

Stubs are essential for testing because they help to isolate modules, allowing developers and testers to verify that each component behaves as expected even when its dependencies are not fully realized. This isolation can lead to more focused testing efforts and help identify issues early in the development process before the full system is complete.