Software updates can be tricky – fix one bug or add a new feature, and suddenly, something else stops working. It's like pulling a loose thread on a sweater: you never know what might unravel. That's the role of regression testing: to make sure your changes don't accidentally create new problems. However, not all regression tests tackle the same issues.
In this post, we'll go over 9 types of regression testing, when to use each, and how they can keep your software intact.
Why are there different types of regression testing?
You might wonder, "If the goal is to ensure nothing breaks, why do we need multiple types?" The answer is simple – complexity. Software is built on layers of interconnected modules, services, and dependencies. Depending on the changes introduced, different testing approaches are required. Some might need thorough, exhaustive checks, while others just need to focus on specific areas.
So, let's take a closer look at all the types of regression testing that every software tester should be familiar with:
1. Corrective regression testing
Starting with the most straightforward type, corrective regression testing is conducted when no changes are made to the existing software specifications. The primary objective is to validate that the software works exactly as it did before, using the same test cases without any updates or modifications.
When to use
For instance, in a scenario where you've just refactored the codebase for performance optimization or cleaned up redundant code – no new functionalities or features were added. This is the perfect use case for corrective regression testing, as it ensures that code reorganization or optimization hasn't altered any behavior.
Example
Consider a large e-commerce site that optimizes its backend database queries for faster product searches. Since the search algorithm and UI remain unchanged, the QA team can run a corrective regression test using the same test cases as before. This type of regression testing confirms that performance has improved without altering the search results or introducing errors.
2. Retest-all regression testing
Next up is retest-all regression testing, which involves a comprehensive approach. It's considered the "all-inclusive strategy" of regression testing – exhaustive and resource-intensive. It includes retesting the entire application, covering all modules and components. While this method is very thorough, it's typically used only when critical areas are modified or when the software undergoes a major update.
When to use
You would opt for retest-all when multiple critical areas are modified or if the software has undergone a major architectural shift. For example, if a financial application switches its entire reporting module to a new framework, it might be necessary to ensure that no part of the application is impacted.
Example
Picture a hotel booking platform that migrates its entire inventory management system to a new technology stack. Since this affects every area of the software – from room availability to booking confirmation – the QA team uses a retest-all approach to verify that all workflows continue to function as expected.
3. Selective regression testing
In contrast to the "all-inclusive strategy," selective regression testing is a more focused approach. It involves testing only a subset of the test cases, targeting the specific areas directly impacted by recent changes. This approach saves both time and resources, making it an efficient choice for smaller updates.
When to use
This type of testing is particularly useful when the scope of changes is limited. For example, if a bug fix affects only the payment gateway of an e-commerce platform – there's no need to test the entire site. Instead, you would run tests related to the payment process and a few surrounding modules.
Example
Think of a subscription-based streaming service integrating a new video player. Rather than testing every single feature, the QA team focuses on video playback, buffering, and streaming quality while skipping unrelated features like user profiles and account settings.
4. Progressive regression testing
Moving on, progressive regression testing is relevant when there are changes to the software's specifications or when new functionalities are added. Since new code is integrated, the old test cases often need to be updated or modified to reflect these changes accurately.
When to use
You'd typically use progressive regression testing when a product undergoes feature enhancements or specification changes. Without this type of testing, existing test cases might become outdated, potentially missing defects in the newly integrated features.
Example
Let's say an e-learning platform introduces a new "Live Class" feature while keeping its core course content delivery system intact. The QA team updates existing test cases for course navigation and student assessments to accommodate the new feature, ensuring it doesn't disrupt current functionality.
5. Partial regression testing
Sometimes, changes affect only a minor portion of the software. This is where partial regression testing shines. It verifies that recent modifications only affect the parts they were supposed to without impacting the rest of the system.
When to use
Partial regression testing is most effective for small tweaks, bug fixes, or code patches. It's especially helpful when you want to ensure that a small change hasn't unexpectedly rippled through the rest of the application.
Example
Consider an online food delivery app that fixes a bug causing discount codes to malfunction. The QA team conducts partial regression testing, focusing only on the discount application and checkout modules to verify that the issue is resolved without introducing new errors.
6. Unit regression testing
Shifting gears a bit, unit regression testing zeroes in on a specific unit or code level. This type of regression testing ensures that the isolated code unit works as expected without considering its interactions with other components.
When to use
You'd opt for unit regression when a developer makes changes to a small part of the code, such as a function or class, and needs to validate that the new code performs correctly.
Example
Imagine a developer working on a weather forecasting app that refactors a function responsible for converting temperature units. The QA team tests unit regression to ensure the function handles various input types and edge cases accurately.
7. Complete regression testing
Complete regression testing, on the other hand, offers a holistic approach. That means testing the entire system, especially when multiple modules are impacted or when the software has undergone substantial changes.
When to use
Complete regression testing is appropriate for major releases or when the software has undergone architectural changes. It's also used when establishing a new baseline of functionality before moving forward.
Example
Picture a finance management system that revamps its user interface and reporting modules. The QA team opts for complete regression testing to verify that all parts of the application – user management, transaction tracking, and report generation – function correctly after the update.
8. Automated regression testing
Automated regression testing is perfect for repetitive tasks and large-scale applications. Automated tools run predefined test cases every time there's a new code deployment, saving time and reducing human error.
When to use
Automation is a lifesaver for teams that release updates frequently and need to prevent old bugs from reappearing.
Example
Think of a large-scale CRM software that automates its regression tests using tools like Selenium to cover scenarios such as lead creation, opportunity tracking, and sales forecasting.
9. Manual regression testing
Last but not least, manual regression testing involves human testers running test cases manually. This method is more flexible and useful for scenarios that are difficult to automate, such as UI testing or user experience exploration.
When to use
Manual regression testing is used when automated tools can't capture nuanced user experiences or when exploratory testing is needed.
Example
After a redesign of the user interface for a fitness tracking app, manual testers explore various user flows to ensure that navigation feels intuitive and users can easily set up workouts and view activity history.
How can Global App Testing support your regression testing?
Global App Testing (GAT) guides teams through every phase of the testing lifecycle, helping elevate your application’s quality from good to exceptional.
Our focus on thorough testing and efficient workflows ensures usability enhancements, higher stakeholder value, and smooth development cycles.
Key benefits of using GAT for regression testing:
- Our platform features a user-friendly interface, making it easy for teams to create, manage, and track test cases effortlessly.
- With a community of over 90,000 skilled testers worldwide, GAT guarantees comprehensive test coverage across diverse devices, operating systems, and geographies.
- GAT’s average turnaround time of 60–150 minutes ensures swift feedback, enabling teams to address issues without delays.
- Our testing capabilities are available around the clock, allowing teams to run tests whenever needed, supporting agile development practices.
- GAT transforms complex testing data into actionable insights, making it easy to identify and resolve issues quickly.
- Receive comprehensive bug reports within 24–36 hours, complete with video recordings, screenshots, and step-by-step reproduction paths to facilitate faster issue resolution.
- GAT integrates smoothly with popular project management tools such as Jira, TestRail, Zephyr, and GitHub, enhancing team collaboration and efficiency.
- Adhering to ISO/IEC 27001 standards, GAT ensures your testing process is secured with robust security protocols to protect sensitive data.
Our regression testing is executed by experienced QA engineers and testers, ensuring thorough validation of your application with each new update. This process minimizes the risk of defects being reintroduced, allowing your development team to concentrate on innovation and feature development.
Ready to elevate your app's quality? Contact our QA specialists to learn how GAT can make your product bug-free and user-friendly!
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