Regression Testing

What is Regression Testing ?

Ensuring that a bug is fixed without any side effect is called Regression Testing .
Or
Testing the functionality of unchanged feature to make sure that it is not broken because of the changes .

The Re-execution of selected test cases on modified build to estimate completeness and correctness
of the application without any ripple effects due to bug fixes . 

Regression Testing is required when there is a

• Change in requirements and code is modified according to the requirement
• New feature is added to the software
• Defect fixing
• Performance issue fix