Regression Testing - Software Engineering

Last Updated : 17 Jun, 2025

Regression Testing is a crucial aspect of software engineering that ensures the stability and reliability of a software product. It involves retesting the previously tested functionalities to verify that recent code changes haven't adversely affected the existing features.

By identifying and fixing any regression or unintended bugs, regression testing helps maintain the overall quality of the software. This process is essential for software development teams to deliver consistent and high-quality products to their users.

What is Regression Testing?

Regression testing is like a software quality checkup after any changes are made. It involves running tests to make sure that everything still works as it should, even after updates or tweaks to the code. This ensures that the software remains reliable and functions properly, maintaining its integrity throughout its development lifecycle.

When to do regression testing?

Regression testing is necessary in several scenarios to maintain software quality:

When new functionality is added to the system and the code has been modified to absorb and integrate that functionality with the existing code.
When some defect has been identified in the software and the code is debugged to fix it.
When the code is modified to optimize its working.

Process of Regression testing

Firstly, whenever we make some changes to the source code for any reason like adding new functionality, optimization, etc. then our program when executed fails in the previously designed test suite for obvious reasons. After the failure, the source code is debugged to identify the bugs in the program. After identification of the bugs in the source code, appropriate modifications are made.

Process-Regression-testing — Process Regression testing

Then appropriate test cases are selected from the already existing test suite which covers all the modified and affected parts of the source code. We can add new test cases if required. In the end, regression testing is performed using the selected test cases.

Here is the step-by-step process of the regression testing:

Identify Code Changes: Analyze the source code to determine which areas have been modified, such as new features, bug fixes, or optimizations.
Debug and Fix Failures: If existing test cases fail due to changes, debug the code to identify and resolve defects.
Modify Code: Apply necessary updates to the code to incorporate changes or fixes.
Select Test Cases: Choose relevant test cases from the existing test suite that cover modified and affected areas. Add new test cases if needed to address new functionality.
Execute Regression Tests: Run the selected test cases, either manually or using automated tools, to verify system behavior.
Analyze Results: Review test outcomes to identify regressions, document issues, and recommend fixes.
Retest as Needed: If defects are found, fix them and re-run tests to confirm resolution.

Techniques for the selection of Test cases for Regression Testing

Selecting the right test cases is critical for efficient regression testing. Common techniques include:

Select all test cases: In this technique, all the test cases are selected from the already existing test suite. It is the simplest and safest technique but not very efficient.
Select test cases randomly: In this technique, test cases are selected randomly from the existing test suite, but it is only useful if all the test cases are equally good in their fault detection capability which is very rare. Hence, it is not used in most of the cases.
Select modification traversing test cases: In this technique, only those test cases are selected that cover and test the modified portions of the source code and the parts that are affected by these modifications.
Select higher priority test cases: In this technique, priority codes are assigned to each test case of the test suite based upon their bug detection capability, customer requirements, etc. After assigning the priority codes, test cases with the highest priorities are selected for the process of regression testing. The test case with the highest priority has the highest rank. For example, a test case with priority code 2 is less important than a test case with priority code.

Top Regression Testing Tools

In regression testing, we generally select the Test Cases from the existing test suite itself and hence, we need not compute their expected output, and it can be easily automated due to this reason. Automating the process of regression testing will be very effective and time-saving. The most commonly used tools for regression testing are:

1. Selenium

Open Source: Selenium is an open-source tool, making it freely available and accessible for developers and testers.
Browser Compatibility: Supports multiple browsers, including Chrome, Firefox, Safari, and Edge, ensuring tests can be run across different environments.
Programming Language Support: Allows writing tests in various programming languages such as Java, Python, C#, Ruby, and JavaScript, providing flexibility for testers.
Cross-Platform: Capable of running on different operating systems, including Windows, macOS, and Linux, which enhances the tool’s portability.
Web Application Testing: Primarily designed for automating web applications, making it ideal for regression testing of web-based systems.
Extensive Community Support: Boasts a large and active community, offering a wealth of resources, plugins, and extensions to aid in test automation.
Integration Capabilities: Integrates well with other tools such as Jenkins for continuous integration and continuous deployment (CI/CD), facilitating automated regression testing in development pipelines.

2. Ranorex Studio

Comprehensive Testing Solution: Ranorex Studio provides a complete testing solution that supports end-to-end regression testing, including both functional and non-functional tests.
User-Friendly Interface: The tool offers an intuitive and user-friendly interface, making it accessible for both beginners and experienced testers.
Cross-Platform Testing: It supports cross-platform testing, enabling tests to be executed on desktop, web, and mobile applications, ensuring broad test coverage.
Codeless Test Automation: Ranorex Studio offers codeless automation through its capture-and-replay functionality, allowing testers to create automated tests without extensive programming knowledge.
Robust Reporting: The tool provides detailed and customizable test reports, helping teams to easily identify issues and track the quality of the software over time.
Integration Capabilities: It integrates seamlessly with popular development and CI/CD tools such as Jenkins, Azure DevOps, and Git, promoting a streamlined workflow and continuous testing.
Data-Driven Testing: Ranorex Studio supports data-driven testing, allowing testers to run the same set of tests with different data inputs, enhancing test coverage and reliability.

3. testRigor

AI-Powered Test Automation: testRigor utilizes artificial intelligence to automate the creation and maintenance of regression tests, reducing the effort and time required for manual testing.
Natural Language Processing (NLP): The tool allows users to write test cases in plain English, making it accessible to both technical and non-technical team members. This feature simplifies test creation and improves collaboration.
Codeless Test Creation: Users can create and execute test cases without writing any code, which speeds up the testing process and reduces the dependency on developers.
Cross-Browser and Cross-Platform Testing: testRigor supports testing across multiple browsers and platforms, ensuring that the software works consistently in different environments.
Self-Healing Tests: The tool automatically updates test scripts to adapt to minor changes in the application's UI, minimizing the maintenance overhead commonly associated with regression testing.

4. Sahi Pro

Cross-browser Testing: Supports multiple browsers, ensuring consistent performance across different environments.
Ease of Use: User-friendly interface with scriptless record and playback functionality, making it accessible for testers with varying levels of expertise.
Robust Reporting: Detailed reports and logs that help in tracking and analyzing test results efficiently.
Integrated Suite: Offers integration with various Continuous Integration (CI) tools like Jenkins, enhancing the automation workflow.
Scalability: Capable of handling large-scale test automation projects with ease.
Script Flexibility: Supports both scriptless testing and advanced scripting using JavaScript, providing flexibility for complex test scenarios.

5. Testlio

Global Network of Testers: Access to a diverse pool of professional testers from around the world. Ensures comprehensive test coverage across different devices, operating systems, and locations.
On-Demand Testing: Flexible scheduling allows for testing when needed, fitting into the development cycle seamlessly. Enables quick turnaround times for regression testing after code changes.
Integrated Platform: Combines test management, test execution, and reporting in a single platform. Simplifies the regression testing process and provides a centralized view of test results.
Comprehensive Reporting: Detailed reports with actionable insights. Helps identify and prioritize issues, making it easier to address regressions promptly.

Advantages of Regression Testing

Regression testing offers benefits that enhance software quality and development efficiency:

Automated unit testing.
Comprehensive test coverage.
System integration.
Faster test execution completion.
Improved developer productivity.
Parallel testing.
Reduced costs.
Regression testing improves product quality.
Reusability.
Scalability.
Time efficiency.

Disadvantages of Regression Testing

Regression testing has some challenges which is follows:

It can be time and resource-consuming if automated tools are not used.
It is required even after very small changes in the code.
Time and Resource Constraints.
Among the significant risks associated with regression testing are the time and resources required to perform it.
Incomplete or Insufficient Test Coverage.
False Positives and False Negatives.
Test Data Management Challenges.

Conclusion

Regression testing is like a safety net for software changes, making sure they do not bring in new problems. It picks test cases from existing suites, sometimes focusing on modified parts. Popular tools like Selenium and QTP automate this process. While it ensures thorough testing, doing it manually can up time and encounter data management issues.

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