What is the difference between unit testing and integration testing in QA testing?

Unit testing and integration testing are both important components of QA testing, but they serve different purposes.

Unit Testing:

• Unit testing involves testing individual units or components of a software application in isolation.
• It focuses on validating the functionality of each unit/module independently from other parts of the application.
• Unit tests are usually conducted using mock objects or stubs to isolate the unit being tested.
• It helps in identifying bugs or issues at an early stage of development.

Integration Testing:

• Integration testing involves testing the interactions between different components or modules of a software application.
• It aims to identify any issues that may arise when the integrated units interact with each other.
• Integration testing ensures that the units work together as expected and the data flows correctly between them.
• It is usually performed after unit testing and focuses on the relationships between units.

In summary, unit testing is focused on testing individual units in isolation, while integration testing is focused on testing the interactions between different units. Both types of testing are essential for ensuring the quality and reliability of a software application.