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Regression Testing

Regression Testing is the process of re-testing existing and previously working functionality to ensure that new changes (bug fixes, enhancements, or code changes) have not introduced new defects.

Regression testing answers: “Did the recent change break anything that was already working?”

1. Definition

Regression Testing is the process of re-testing existing and previously working functionality to ensure that new changes (bug fixes, enhancements, or code changes) have not introduced new defects.

Regression testing answers: “Did the recent change break anything that was already working?”

2. Purpose of Regression Testing

  • Ensure application stability after changes
  • Detect unintended side effects
  • Protect existing functionality
  • Maintain product quality over time

3. When Regression Testing Is Performed

  • After defect fixes
  • After new feature implementation
  • After configuration changes
  • Before major releases

4. Scope of Regression Testing

Regression testing includes:

  • Core business functionalities
  • High-risk areas
  • Previously defect-prone modules
  • Impacted and dependent features

5. Manual Tester’s Role

  • Identify regression test cases
  • Execute regression suites manually
  • Log regression defects
  • Maintain regression test documentation

6. Types of Regression Testing (Manual)

6.1 Partial Regression

  • Test impacted areas only

6.2 Full Regression

  • Test entire application

6.3 Selective Regression

  • Test high-risk and critical features

7. Regression Testing vs Re-Testing

Aspect Regression Testing Re-Testing
Focus Existing functionality Fixed defect
Scope Broad Narrow
Test cases Different Same
Automation Optional Not applicable

8. Real-Time Example

Fix applied to login module:

  • Re-test login defect
  • Regression test registration, profile, logout

9. Entry & Exit Criteria (Regression Testing)

Entry Criteria

  • New build with changes available
  • Regression test cases identified

Exit Criteria

  • Regression cases executed
  • No critical regression defects

10. Common Regression Defects

  • Broken workflows
  • Unexpected UI issues
  • Data corruption
  • Side effects in dependent modules

11. Common Mistakes

  • Skipping regression due to time pressure
  • Testing only changed feature
  • Poor regression test selection

12. Interview-Ready Answers

Short answer:

Regression testing ensures that existing functionality works correctly after changes are made.

Detailed answer:

Regression testing verifies that new code changes do not negatively impact previously working features.

13. Key Takeaway

Regression Testing is essential to protect product stability during continuous change.