What is the difference between unit testing and integration testing?

Unit testing and integration testing are two different levels of testing in the software development process.

Unit testing focuses on testing individual components or units of code in isolation. It is typically done by developers and involves testing small, specific functionalities or methods within a module or class. Unit tests are written to verify that each unit of code works as expected and meets the specified requirements. Mock objects or stubs may be used to simulate dependencies and isolate the unit being tested.

On the other hand, integration testing is performed to test the interaction and integration between different components or modules of a system. It aims to identify any issues or bugs that may arise when multiple units are combined and working together. Integration testing ensures that the different units of code can communicate and function correctly as a whole system. It may involve testing the interfaces, data flow, and interactions between various components.

In summary, the main difference between unit testing and integration testing lies in their scope and focus. Unit testing is concerned with testing individual units of code in isolation, while integration testing focuses on testing the interaction and integration between multiple units or components.