Testing the unchanged features to make sure that it is not broken because of the changes (changes means – addition, modification, deletion or defect fixing).
When the development team gives a build, chances are there that they might have done some changes. That change might affect unchanged features. So, Testing the unchanged features to make sure that it is not broken because of the changes is called Regression Testing.
Unit Regression Testing
Regional Regression Testing
Full Regression Testing
Here, we are going to test only the changes.
In Build B01, a bug is found and a report is sent to the developer. The developer fixes the bug and also sends along some new features developed in the second build B02.
Testing only the modified features is called Unit Regression Testing.
Testing the changes and impact regions is called Regional Regression Testing.
After two releases of the product, during the third release – customers might ask for adding two new features, deleting one feature and modifying another feature. Also some bugs might need to be fixed. The testing team after doing impact analysis finds out that making all the above changes will lead to testing the entire product.
Thus, Testing the changes and all the remaining features is called Full Regression Testing.