Comparison between Regression Testing and Re-Testing – Software Engineering

This article focuses on discussing the comparison between Regression Testing and Re-Testing.

What is Regression Testing?

Regression Testing is a type of software testing, which is used to verify that modifications in the software or the environment have not caused any unintended adverse side effects. 

1. This technique involves retesting the entire system or a part of the system to ensure that the existing functionality of the software is still working as expected after making changes.
2. Regression testing can be performed manually or using automated tools.
3. Regression testing is performed after making any change in the software system, including bug fixes, enhancements, or new features.

What is Re-testing?

Retesting is done to make sure that the bug is fixed and whether the failed functionality is working fine or not, this is a kind of verification method followed in the testing field for the fixed bugs. Most of the testers have confusion with Regression and Retesting. 

1. Regression testing and re-testing are two important software testing techniques that are used to ensure the quality and reliability of software applications.
2. Although both techniques involve retesting software, there are some key differences between the two approaches.
3. Re-testing involves retesting a specific part of the software that was previously identified as having a defect.
4. Re-testing is typically performed after a bug has been fixed, and the software has been reworked to address the defect.
5. The objective of re-testing is to ensure that the specific issue that was previously identified has been resolved, and the software now works as expected.

Regression Testing vs Re-testing

Parameters	Regression Testing	Retesting
Known As	Regression testing is known as a generic testing.	Retesting is known as planned testing.
Objective	Regression testing is to ensure that changes have not affected the unchanged part of product.	Retesting is used to ensure the test cases which failed in last execution are fixed. It is performed on a specific part of the system to verify that a specific defect has been fixed.
Scope	Regression testing is used for past test cases. It is performed on the entire system or a subset of the system to ensure that all previously tested functionality is still working as expected	Retesting is used only for failed test cases.
Defect Verification	Defect verification is not coming under regression testing.	Defect verification is coming under retesting.
Manual/ Automation Testing	Regression testing can be done either in automation or manual testing.	Retesting can not be automated.
Priority	Regression testing has lower priority than retesting testing but in some cases it can be done in parallel with retesting.	Retesting has higher priority than regression testing.
Test Cases Executed	Passed test cases can be executed during regression testing.	Only failed test cases are re-executed during retesting.
Test Case Automation	During regression testing test cases can be automated.	During retesting test cases can’t be automated.
Time	It takes more time as it explores the whole application to uncover the bugs.	It takes less time as it focuses only on the exploration of a certain defect of the product.
Need	Testing for regression is done to look for unanticipated side effects.	To ensure the functioning of original problem as expected retesting is carried out.
When to Perform?	Regression testing is only performed after a code modification, in case of implementation of a new feature, or an enhancement.	Retesting is performed in the same environment and with the same data, but a new build is used.
Source of Test Cases	Test cases are obtained from the document specification and bug reports.	Test cases are not obtained beforehand but only after the start of testing.
Pros	Significant role in agile environment in ensuring continuity of business operations. Aids in identification of bugs in the software Constant additions will not hamper the integrity of application Helps in achieving higher CSI (Customer Satisfaction Index) Reduction in unnecessary expenses It can be implemented both ways-manually or automatically. Helps in detection and fixing of bugs	Verification of the resolved issue and is functioning as intended. Verification time is less because it is only limited to the specific issue or feature. The level of the program’s or product’s is raised. The same data and environment is used to carry out with the new build.
Cons	Stringent timelines. Optimization of test cases is difficult. Requirement of stable environment. Lack of effective communication between different teams also leads to problems. Selection of right automated tool is crucial for testing. There is slow down in the overall testing.	A new build is needed for the purpose of defect verification. No automation of the test cases. Time consuming because of the re-testing of failed test cases. Test cases can only be obtained after the start of testing and not before that.

In summary, regression testing and re-testing are two important software testing techniques that serve different purposes. Regression testing is used to verify that changes to a software system do not have unintended consequences while re-testing is used to verify that specific defects have been resolved. Both techniques are critical to ensuring the quality and reliability of software applications.