Regression Testing and Retesting

Difference between Regression Testing and Retesting is another one of the most frequently asked question in Software Testing interviews. So, a very straight forward and crisp answer would be –
Re-testing is the verification of defects to confirm that the functionalities are working as expected. When a bug is fixed, the test cases which failed with reference to it are executed again.
Regression Testing is performed to verify that any changes to the code (bug fixes, enhancements, code cleanup etc.) have not impacted the untouched or other functionalities of the software/application.
For example:

  • Consider an application ‘abc’ with modules ‘a1, b1 and c1’.
  • Some bug fixes are to module b1.
  • Retesting – Testing the bugs raised and module b1.
  • Regression Testing – Testing the areas affected by module b1 on a1 and c1.

Regression Testing
Image Source: MS Word Clip Art
The image above also represents basic Regression Testing and Retesting concept:
Rotten apple spoils the barrel –
Ensure the rotten one is removed ~Re-testing
Always go through the rest ~Regression Testing
Following is a detailed description of differences between Regression and Retesting.


Regression Testing

Retesting is performed to make sure that the tests cases which failed in last execution are passed after the defects against them failures are fixed.
Regression testing is performed to ensure that changes like defect fixes or enhancements to the module or application have not affected the unchanged parts of application.
Retesting is carried out based on the defect fixes.
Regression testing is not carried out on specific defect fixes. It is planned as specific area or full regression testing.
In Retesting, the test cases which failed earlier are included in the test suite.
In Regression testing, test cases which impact the functionality of application are included in the test suite irrespective of their passed/failed status in earlier runs.
Test cases for Retesting cannot be prepared before start testing. In Retesting only re-execute the test cases failed in the prior execution.
Regression test cases are derived from the functional specification, user manuals, user tutorials, and defect reports in relation to corrected problems.
Automation for retesting scenarios is not recommended.
Regression scenarios are the first candidates of automation testing
Retesting is performed before Regression.
Regression testing can be carried out parallel with Retesting.


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