How we can explain Regression testing Vs Functional Testing?

Regression testing and functional testing are both essential aspects of software testing, but they serve different purposes and focus on different aspects of the software. Here's an explanation of each:

Regression Testing:

1. Purpose: Regression testing ensures that recent code changes or modifications to an application haven't introduced new defects or caused existing functionalities to fail.
2. Scope: It involves re-executing select test cases from the existing test suite to verify that previously developed and tested features still function correctly after changes have been made.
3. When to Perform: Regression testing is typically performed after code modifications, bug fixes, or the addition of new features to the software to ensure that the overall integrity of the system is maintained.
4. Focus: The primary focus of regression testing is to detect and mitigate any unintended side effects or regressions introduced by changes to the codebase, without necessarily retesting all functionalities comprehensively.

Functional Testing:

1. Purpose: Functional testing evaluates the behavior of the software against its specified requirements and functional specifications.
2. Scope: It involves testing each functionality or feature of the software to ensure that it behaves as expected and meets the desired functionality outlined in the requirements documentation.
3. When to Perform: Functional testing is typically performed throughout the development lifecycle, starting from the early stages of development and continuing through to release and maintenance.
4. Focus: The primary focus of functional testing is to verify that the software performs its intended functions correctly, including input validation, output generation, data manipulation, and interaction with other system components.

In summary, while both regression testing and functional testing are essential for ensuring the quality and reliability of software, they differ in their purpose, scope, and focus. Regression testing primarily checks for unintended consequences of changes, while functional testing focuses on validating the functionality of the software against its specified requirements.