What is Regression Testing: Definition, Types, Examples

Updating a complex codebase can introduce unexpected bugs, and regression testing is essential to ensure that new changes don’t break existing functionality.

In 2024, UK banks experienced 158 IT failures, and Barclays alone may face £12.5 million in compensation, underscoring the risks of outdated systems and insufficient testing. Many of these issues could have been avoided with thorough regression testing before release.

In this blog, we’ll explore what automated regression testing is, the different 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.

“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

Why is Regression Testing Important?

Regression testing ensures that updates don’t disrupt existing functionality, maintaining software stability. Here’s why it matters:

• Ensures Stability: Validates that new updates or changes don’t interfere with existing functionality, ensuring the software remains consistent and reliable across versions.
• Catches Hidden Bugs: Even minor changes can cause unexpected issues in unrelated parts of the application. Regression testing helps uncover these problems early.
• Automates Efficiency: Regression testing can be automated to accelerate validation, reducing manual effort while maintaining accuracy.
• Ensures Consistent User Experience: Users expect apps to work seamlessly. Regression testing helps prevent issues like broken logins or forms, maintaining trust with every release.
• Builds Confidence in Releases: With a reliable regression suite in place, teams can ship faster and more often without worrying about what might break.
• Reduces Cost of Fixes: Bugs found late in the development cycle—or after release—are more expensive to fix. Regression testing keeps the cost of quality low by catching issues early.
• Supports Long-Term Product Quality: As your application grows, so does its complexity. Regression testing helps maintain quality over time, keeping technical debt under control.

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.

1. Understand What’s Changed: 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.
2. Identify and Prioritize Test Cases:
• High priority: Core features, recent code changes, and areas with a high risk of defects based on business criticality, high user frequency, or past failure history.
• Medium priority: Non-critical features like field validations and negative test cases.
• Low priority: UI elements like logos, button texts, and non-essential functions.
3. Choose the Right Automation Tool:
• Choose a suitable framework: Choose a framework that fits your application type—web, mobile, or API—and integrates seamlessly with your existing workflows
• Script efficiently: Convert your test cases into reusable, maintainable scripts. Keep them modular and descriptive.
• Use a cloud grid: Use LambdaTest for scalable, on-demand test environments. Run tests in parallel to accelerate execution across multiple browsers and devices.
4. Integrate with CI/CD: Integrate with CI/CD to run tests automatically on every commit and catch issues early in the pipeline.
5. Analyze Results & Fix Failures: Execute automated tests and review the results to identify failures. Log real bugs quickly for resolution and use dashboards to track trends and spot flaky tests.
6. Maintain & Update Tests Regularly:
• Update outdated scripts: Modify or remove tests that no longer reflect current functionality.
• Add new coverage: Ensure new features and edge cases are properly tested over time.
• Optimize test suite: Continuously refine your regression suite for speed, accuracy, and relevance.

Top Regression Testing Tools and Frameworks

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.

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.

3. Appium: An open-source tool for automating regression tests on mobile apps, supporting native, hybrid, and mobile web apps across Android and iOS using real devices or emulators with Appium.

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:

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.

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.

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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