In what cases and for what purposes is unit testing used?

Unit testing is used to verify individual components (modules) of an application in isolation from the rest of the system. The goals:

• Detect errors early in the development process.
• Ensure the correctness of specific functions or classes.
• Simplify debugging and maintenance.
• Allow quick testing of changes without running the entire application.

In Android, unit tests are usually written for business logic, utilities, ViewModel, and other components that do not depend on UI or platform services. This helps ensure that individual parts of the application work correctly regardless of external factors.