What is Regression Testing: Definition, Types, Examples

Updating a large and complex codebase can be challenging. When adding new features, fixing bugs, or improving what’s already there, there’s a chance of accidentally affecting the application’s functionality, whether it’s a mobile app, a web application, or a website.

In January 2012, Marks & Spencer faced a major financial setback due to a software pricing error. Televisions that were meant to be listed at £1,099 appeared online for just £199—a staggering miscalculation that led to significant revenue loss and reputational damage.

This pricing glitch could have been prevented with thorough regression testing before release. By systematically verifying software updates, businesses can avoid costly mistakes, protect profits, and maintain consumer trust

In this blog, we will learn what automated regression testing is, its types, and how it works.

What is Regression Testing?

Regression testing is a software testing process conducted after code changes to ensure new updates don’t negatively impact existing functionalities. It helps identify whether new or reemerging bugs are introduced, maintaining software stability and performance consistency.

Automated regression testing helps developers identify and fix recurring issues caused by new code changes. It ensures the software remains reliable and stable throughout the entire development lifecycle.

The graph illustrates how regression testing and new feature testing progress through different software versions.

• Regression Testing (F1, F2, F3, F4) is performed at each stage (V1 to V4) to ensure that new changes don’t break existing functionality.
• New Feature Testing (F1, F2, F3, F4) runs concurrently to validate new additions without disrupting the overall software.

This overlap ensures software stability while incorporating new features.

Why is Regression Testing Important?

Any software change—be it bug fixes, new features, or tweaks—can introduce new issues. Regression testing ensures that updates don’t disrupt existing functionality, maintaining software stability.

Example – Tesla

On the front page of Tesla.com, you can see all Tesla’s products.

When Tesla adds a new product like the Cyber Truck to their website, it’s crucial to ensure that the new UI flow doesn’t disrupt existing ones and that the rest of the product UI flows continue to work functionally as before.

A regression test suite, run manually or automated with tools like Selenium, checks for this. If a test fails, it indicates a broken feature that needs immediate attention. The regression suite should be executed whenever UI changes are made and continuously updated to cover more UI flows, ensuring the website remains stable and functional.

“Regression testing is considered easy when viewed from a distance, but the reality is, it’s much more complex. It’s not just about repetition; it’s about ensuring all aspects of your system are properly tested.” –Rahul Verma, Consulting Tester and Coach from Trendig GmbH

When to Perform Regression Testing?

Regression testing is necessary whenever changes are made to the software to verify that the updates do not cause unintended issues with existing features. Key situations to perform regression testing include:

1. Bug Fixes: After fixing bugs to ensure that the fix doesn’t affect other areas of the application.
2. New Features or Enhancements: When new features are added or existing ones are enhanced, regression tests ensure that other parts of the software remain unaffected.
3. Code Refactoring: When the codebase is refactored to improve performance or maintainability, regression testing verifies that no unintended side effects occur.
4. Software Updates or Patches: When applying software updates or security patches, regression testing ensures the update doesn’t break existing functionality.
5. Integration with New Systems: When integrating the software with new systems, regression testing ensures compatibility and stability.
6. Before Production Releases: Prior to releasing a new version to production, regression testing ensures the software is stable and fully functional.

How to Perform Automated Regression Testing?

Regression tests can be executed both manually and in an automated manner. Test Engineers primarily use special techniques and methods to perform Regression tests.

Below are the phases involved in Regression testing –

1. Test Case Selection: The selection of test cases is determined by the component, one with a massive number of code modifications. Testers can split the tests into two categories: reusable test cases and obsolete test cases. Reusable test cases will be used in future Regression test cycles, but obsolete test cases will not be considered in further Regression test cycles.
2. Time Estimation: Following the selection of test cases, the next step is to estimate the test execution time. Test case generation, test case evaluation, and other factors impact test execution time.
3. Automate Test Cases: Testers should select between manual and automated Regression tests based on the number of test cases after time estimation.
4. Test Case Prioritization: In this step, testers prioritize test cases based on recent code changes, minimizing Regression time and effort. The test cases with high priority are executed first, followed by medium and low priority.
5. Test Execution: Finally, all test cases are run in the order of priority to find flaws and ensure that the application is functioning correctly. Automated regression testing tools like Selenium enable you to reduce test execution time and automate your Regression test suites more quickly.

Selecting Test Cases for Regression Testing

Here’s how to prioritize regression test cases:

Below are the steps to select regression test cases:

1. Test Cases with Frequent Issues: Focus on areas that are prone to defects. These are often the parts that are most susceptible to breaking with new code changes.
2. Core Functionalities: Prioritize test cases that cover essential features such as payment systems, search functions, and key workflows that users rely on.
3. Areas Affected by Recent Changes: Any new code or features should be tested thoroughly as they are most likely to introduce defects.
4. User Interface (UI): Test critical UI elements like buttons, links, and logos to ensure they perform correctly across different devices and platforms.
5. Integration Scenarios: Focus on components that depend on each other, as changes in one area can affect the functionality of others.
6. Complex Test Cases: Prioritize complex scenarios that might cause crashes or slow performance.
7. Risk-Based Testing: Focus on high-risk areas based on recent changes, which can help reduce overall testing time and effort.

Categorizing Regression Test Case Priorities:

• High priority: Core features, recent code changes, and areas with a high risk of defects.
• Medium priority: Non-critical features like field validations and negative test cases.
• Low priority: UI elements like logos, button texts, and non-essential functions.

By strategically selecting and prioritizing test cases, you can ensure that your regression testing is efficient and effective, maintaining software stability and performance.

Top Regression Testing Tools

Here are some tools that can be useful for creating and executing Regression tests. However, the requirements of each product should be thoroughly studied before deciding which ones to use.

1. LambdaTest

LambdaTest is an AI-native test orchestration and execution platform that lets you run manual and automated tests at scale with over 10,000+ real devices, browsers, and OS combinations. LambdaTest incorporates screenshots and video recordings, as well as collaborative and responsive testing options. It is extensively used in the DevOps context for complete cross browser compatibility testing.

2. Selenium

Selenium is an open-source web automation testing tool to test websites and web apps. It is considered one of the top automated Regression tests tools for web application testing. Selenium supports different browsers and platforms for automated browser testing. You can run your automated visual regression tests with Selenium on LambdaTest across 3000+ real browsers and OSes. LambdaTest also allows you to perform Selenium Visual Testing on Cloud that capture and compare screenshots and deliver seamless user experience.

3. Appium

Appium is a powerful, open-source regression testing framework designed for mobile applications, supporting native, mobile web, and hybrid apps. It allows developers to automate their testing workflows across multiple platforms with ease.

With its foundation on the WebDriver protocol, Appium simplifies the process of automating test case execution and validating outcomes. The tool works seamlessly on Android and iOS emulators, simulators, as well as real devices, making it versatile for mobile testing needs.

For a detailed list, also check out this blog where we’ve compiled the top 33 best regression testing tools for comprehensive testing solutions.

Regression Testing Techniques

Depending on your Software Development Life Cycle (SDLC) and the new feature or update you aim to deploy, you can implement various types of regression tests. However, it is essential to understand the several regression tests types to choose the right one.

Below are the different types of regression testing –

1. Corrective Regression Testing: Focuses on testing existing functionality without modifying the codebase. You test existing features rather than creating new test cases.
2. Unit Regression Testing: In unit regression testing, individual code units are tested in isolation, with all other integrations and dependencies disabled.
3. Selective Regression Testing: Assesses the impact of new code on existing elements like functions and variables, quickly identifying issues without affecting the overall process.
4. Progressive Regression Testing: Creates new test cases based on minor product improvements, ensuring updates don’t alter existing functionality.
5. Complete Regression Testing: Used for significant changes, ensuring all areas of the application are tested to catch bugs introduced during updates.
6. Partial Regression Testing: Tests existing code when new code is added, identifying critical bugs without disrupting the system.
7. Retest-all Regression Testing:Re-executes all test cases to ensure no bugs are introduced after code changes, requiring significant effort from the QA team.

Developing Regression Testing Strategy

If you want to make the most of your Regression test suites, it is essential to plan a proper strategy by keeping certain factors in mind. This section discusses some ways to help you create a winning Regression test strategy:

• Execute all existing tests once again: After the product release, Test Engineers must check problem areas again. Many times this can be a challenge, especially when it comes to executing manual testing.
• Run high-priority tests first: About 50% of time spent on regression tests should be devoted to repeating tests that concern the application’s essential functionality.
• Check the complicated features next: Many applications have sophisticated and complicated parts, which can cause problems. Although the functionality is complicated to understand/comprehend, the quality of their functionality must be excellent.
• Execute Exploratory testing: Design new tests based on the new features of the software. Exploratory testing often uncovers hidden bugs not found in scripted tests.
• Test Across Multiple Environments: Always test in a variety of environments, browsers, and devices to ensure cross-platform compatibility. This prevents issues that might arise in specific configurations from affecting the user experience.

Regression Testing at Scale

Incorporating regression testing into the Software Development Life Cycle (SDLC) is vital for ensuring scalability. It necessitates teamwork, consistent processes, and strategic planning. By aligning regression testing with the overall development strategy, teams can synchronize testing efforts, supporting the project’s objectives and delivering stable, high-quality software at scale.

Some other factors to consider:

• Automated Testing: Automated regression testing is crucial for identifying regression bugs promptly due to increased speed and frequency.
• Timely Issue Identification: Detecting issues early prevents defect leakage into the product/application in later testing stages.
• Parallel Testing: This approach provides rapid feedback, allowing teams to generate test results across various environments, browsers, devices, and operating systems.
• Data Migration: When importing legacy data from an older system to a newer one, parallel tests ensure seamless data transfer using an automated regression test suite.

Why is Regression Testing Important in Agile and CI/CD?

Regression testing is essential in Continuous Integration/Deployment (CI/CD) pipelines where code is continuously integrated and deployed. It enables continuous delivery by guaranteeing the stability and dependability of each deployment.

Teams can reduce human overhead by concentrating on more complicated and exploratory testing by automating these tests. Regression testing also encourages teamwork since it gives them confidence in the codebase’s stability, which facilitates a more efficient development process and effective software delivery.

Retesting and Regression Testing: Difference

If you are a beginner in the test automation domain, you might find retesting and Regression Testing to be similar. However, both are different from each other.

Challenges of Regression Testing

Here are a few of the challenges faced by testers:

• Test suite cost and time: A regression test suite needs ongoing updates as new features are added, leading to more test cases. Re-running old and new tests can be time-consuming.
• Complex test cases: As applications grow in complexity, the number and intricacy of test cases increase, consuming more time and resources.
• Maintenance: As applications scale, the test suite becomes more complex, making regular maintenance crucial to manage execution time and complexity.

Best Practices of Regression Testing

Some challenges were covered in the previous section. Now, let’s look at some of the best Regression testing practices.

• Parallel testing: By running tests concurrently across various browsers and OS combinations, parallel testing significantly cuts down on lead time.
• Keep Test Suites Updated: Ensure your regression tests reflect the latest features, verifying that older functionalities still work after updates.
• Use Regression Testing Frameworks: Implement frameworks to streamline maintenance and improve efficiency.
• Cloud-Based Testing: As your application grows, use scalable cloud-based testing infrastructure to manage increasing test requirements.

It helps identify bugs ahead of the deployment deadline. However, as your application becomes more complicated, the number of test cases will expand. As a result, you need a cloud-based testing infrastructure that can scale as your testing requirements grow.

AI-native test orchestration and test execution platforms like LambdaTest help you achieve that. It offers a cloud-scalable infrastructure of 10,000+ real devices, browsers, and OS combinations for your test automation needs. With LambdaTest, you can harness the power of the online Selenium Grid to execute thousands of parallel tests, thereby cutting down your test execution time and getting faster feedback on code changes.

Subscribe to the LambdaTest YouTube Channel and stay updated with the latest tutorials around Selenium testing, Cypress E2E testing, Mobile App Testing Tutorial, and more

In addition to web testing, you can perform mobile app testing on an online device farm of 10,000+ real Android and iOS devices.

Conclusion

Automated regression testing verifies that recent changes in a software application haven’t adversely affected existing functionalities. This efficient approach uses automation tools to run a comprehensive set of tests repeatedly, ensuring stability and functionality post-updates, and providing detailed insights into any failures.

It can be done in many ways, including Corrective Regression testing, Progressive regression testing, Retest-All Strategy, and Selective Strategies. Some tips for strategies pertaining to Regression tests include running high-priority tests first, executing exploratory testing, etc.

Even though Regression tests consume vast amounts of resources, they save your effort and time. It eases the lives of devs and testers in their agile software development lifecycle and yields maximum output.

Devansh Bhardwaj

Devansh works as a Product Marketing Executive at LambdaTest. With a degree in Business Administration and a keen interest in technology, he loves to write about the latest technology trends.

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