Regression Testing

Regression testing is one of the crucial parts of software testing, to verify that the existing functionality of the software works correctly after updates, bug fixes or new features are introduced. When a module is added, modified or upgraded, the same module or related module can be affected due to interdependencies. The primary goal of regression testing is to identify any unintended issues or bugs in these affected parts of the application.

When to Perform Regression Testing

Regression testing is essential after the code changes, as these changes can impact other parts of the application and potentially introduce new bugs. This includes changes from:

-New Features

-Enhancements

-Bug Fixes

In Agile methodology, the development is divided into smaller tasks and completed in iterative sprints. The regression testing should be conducted after a feature is fully developed and integrated, as well as after any significant bug fixes, rather than after every individual code change.

In the Waterfall methodology, where development follows a linear progression, regression testing is focused toward the end of the development cycle.

Key considerations before performing Regression Testing

Before starting regression testing, it is essential to consider these given factors:

Scope of Code Change: Collaborate with the development team to assess how the new code impacts the existing functionality of the application then identify all the areas connected to the updated feature with them.

Business Criticality: Prioritize tests for the areas of the application that are critical for overall business functionality and also align with user requirements.

Historical Defect Density: Prioritize testing in areas known for previous issues and the areas interconnected with many other modules of the application, these areas in the application are likely to get affected easily.

Non-functional Requirements: Non-functional testing is a crucial aspect of regression testing.Even minor code changes can introduce bottlenecks that degrade system speed, scalability, and responsiveness, inadvertently open up security vulnerabilities, and impact accessibility features. It is essential to incorporate non-functional test cases in regression testing to maintain a high standard of quality and reliability.

Selecting Test Cases for Regression Testing

Regression testing is performed to identify unintended bugs in the existing functionality caused by the code change in another part of the application. It may lead us to think any part of the application could be broken due to the code change, so we need to test the entire application to find the affected area. It sounds ideal but impractical. Here are some effective strategies for selecting test cases for regression testing to increase efficiency and resource optimization.

Impacted Area Test cases: Select the test cases that cover the impacted areas of the application because of the new update and touch the updated module of the application.

High-Priority Test Cases: Assign priority to test cases based on their business value, and customer requirements and select it for the regression testing process.

Critical Features Testing: Select the test cases that cover the application’s most-used features, core functionalities, and critical paths, as these are the most vulnerable to code changes.

Regression Testing Process

Collect Required Test Cases: Choose and prioritize appropriate test cases based on the recent code changes and impacted areas. Collect test cases that cover core features and areas with high user feedback or historical defect density.

Test Environment Preparation: Verify test environment has updated code and is ready to test, create all required test data.

Execute Test Cases: After collecting test cases and required test cases, the testing team can execute all the test cases.

Document Results: Document the results, inform the failed tests to the development team, track the bug until they are fixed.

Retest: After the regression bug is fixed, identify test cases directly related to the bug, identify any additional test cases in areas that might be impacted by the fix. Execute these test cases to confirm that the bug is resolved and that the fix hasn’t unintentionally caused new issues in related areas.

Manual vs Automated Regression Tests

Manual Regression Testing

While performing regression testing manually testers needed to execute each test case manually, it has both advantages and disadvantages, let’s see them one by one.

Advantages:

-Effective to catch UI issues and visual defects.

-Even if we missed to update the test cases, we can find the problem simply.

-For small projects with low test cases, manual testing is economical.

 Disadvantages

-Executing all test cases manually takes more time.

-With repetitive tests, testers can become fatigued, which leads to potential oversights.

 Automated Regression Testing

When the application is large and complex, it has thousands of test cases. Performing regression testing for large and complex applications manually takes more time and resources. In automated regression testing, an automation testing tool can execute the test cases.

 Advantages:

-Automation testing is capable of testing the entire application overnight.

-Reduce human error and ensure consistency in test case execution.

-Ideal for an agile environment, Automated testing scales as well as the test suite grows.

-Needs initial investment for writing automation scripts then it saves time and resources in the long run, especially for frequently updated applications.

 Disadvantages:

-Automation testing may miss unexpected bugs and visual and usability issues.

-Automation scripts also need maintenance especially when the application undergoes UI and functionality changes  

Hybrid Approach

Nowadays many teams use the combination of both as automated regression testing for stable and repetitive test cases and manual testing for complex, high-risk, and exploratory test cases. This hybrid approach maximizes efficiency and coverage, ensuring robust regression testing.

Challenges in Regression Testing

Time and Cost Requirements: Regression testing can be time-consuming, especially without automation. As new features are added, the number of test cases increases, requiring more resources to complete testing within the given timeframe.

Test Suite Maintenance: It is essential to keep the test suite up-to-date as the application grows. For every change in the application, the test cases that cover the changes also need to be revived and adjusted based on the changes, which requires ongoing attention and planning.

Risk of Overlooking Bugs: In large and complex applications, certain parts of the system may be unintentionally missed during testing, particularly smaller or less obvious areas. These overlooked parts could contain bugs that go undetected. To avoid this, prioritize test cases and focus on testing the application’s most essential features or areas that would cause major issues if they failed.

Bug Fix and Retesting: Regression bugs often have a higher impact because they indicate that previously working functionality has been affected by recent changes. When a bug is found in regression testing, it’s crucial to rerun the regression tests to confirm the fix and ensure it hasn’t inadvertently affected other areas of the application. This practice minimizes the risk of new issues emerging in already validated features, helping maintain overall software quality and stability.

Conclusion

Regression testing is crucial to make sure that new changes don’t disrupt previously stable parts of the application. By carefully selecting test cases based on code changes, business criticality, customer requirements, and historical defect density, QA teams can efficiently perform regression testing. Ultimately, effective regression testing safeguards the application's reliability, fostering a more seamless user experience and supporting sustainable software growth.