Retesting is a process in software testing where a previously failed test case is tested again after its defects have been fixed. The aim of retesting is to confirm that the defects/bugs have been fixed and that the affected functionality works as expected. Retesting is typically performed by the same testers who identified the defect in the first place. Retesting is different from regression testing, which is designed to test for bugs that are not expected to be there. Some key differences between retesting and regression testing are:

• Regression testing is performed for passed test cases, while retesting is done only for failed test cases.
• Regression testing checks for unexpected side-effects, while retesting makes sure that the original fault has been corrected.
• Regression testing doesn’t include defect verification, whereas retesting includes defect verification.
• Regression testing is known as generic testing, whereas retesting is planned testing.
• Regression testing is possible with the use of automation, whereas retesting is not possible with automation.

Retesting is done when there is a specific bug that needs to be fixed and tested again. It is used to verify the specific bug or issue, confirm to developers that the issue is valid and re-creatable, test the entire module or component to confirm the expected functionality, and check the quality of any particular feature or component or module of an application. Retesting requires a new build for verification of the defect, and the test cases for retesting cannot be automated.