What is Regression Testing? Definition, Tools and Examples

What is Regression Testing?

Regression testing is a testing type to ensure that old features are still working as they should when new features are introduced. New code may bring in new logic that conflicts with the existing code, leading to defects. Usually, QA teams have a series of regression test cases for important features that they will re-execute each time these code changes occur to save time and maximize test efficiency.

If the project does not have a version control system, it can be tricky to locate the exact component that produces the bug. However, with regression testing, we know exactly where the bug comes from, enabling better troubleshooting. It is essentially a periodic health check-up for the software. Due to its highly repetitive nature, regression testing is a great candidate for automation testing.

Examples Of Regression Testing

Keep in mind that regression testing is a practice and method. There isn’t a testing tool for regression testing. Any test that was developed at the initial launch of a certain feature, brought up to run at later releases, is already a regression test. You can have regression tests by application attribute and type:

• Attribute: visual, functional, performance, security
• Application layer: UI and API
• Application type: web, mobile, API and desktop
• Granularity: end-to-end, integration and unit tests (test pyramid)

To perform regular check ups on existing code, regression testing basically involves:

• Testers writing and building automated test suites
• Testers and business analysts filtering out release-specific tests to re-run on affected areas from new releases

Let's consider a detailed example of regression testing for Etsy, an online marketplace for handmade and vintage items.

Etsy has decided to add a new personalized recommendation feature to enhance the user experience. This feature will suggest items based on users’ browsing history, past purchases, and interests. The goal of regression is not to test that new feature. Instead, our goal is to ensure that the new personalized recommendation feature does not disrupt the existing functionality of the website. This means we need to go back to core features to check if they are working as expected after the new feature is integrated.

Here are some test case ideas:

1. Item Listing
2. Search Functionality
3. Cart and Checkout
4. User Account Management
5. Reviews and Ratings
6. Payment Processing

You have 2 approaches to choose from: 

1. Manual regression testing: manually perform all of the test steps and then record results in a test management system.
2. Automated regression testing: leverage automated testing tools like Selenium to create scripts that test core functionalities.
    

Here is a sample test case for search functionality

def test_search_functionality():
    driver = webdriver.Chrome()
    driver.get("https://www.etsy.com")
    
    search_box = driver.find_element_by_name("search_query")
    search_box.send_keys("handmade necklace")
    search_box.submit()
    
    results = driver.find_elements_by_class_name("v2-listing-card")
    assert len(results) > 0, "Search results should not be empty."
    
    driver.quit()

The steps we did include:

1. Open Browser
2. Go to Etsy
3. Find Search Box
4. Enter Search Query ("handmade necklace")
5. Submit Search
6. Check Results
7. Close Browser

Read More: Top Test Cases For Search Functionality

At a larger scale, companies whose business model revolves around their digital products need regression testing to frequently check up on their core features. To improve productivity in regression testing, automation testing tools are commonly employed.

Benefits of Regression Testing

1. Prevents Domino Effect on Key Functions: Even minor modifications in the code can cause significant issues in the product’s key functionalities. Regression testing helps detect these issues early, preventing extensive efforts to reverse the damage.
    
2. Aligns with Agile Methodology: Regression testing supports Agile practices by continuously iterating, integrating, and testing new code. This leads to frequent releases and faster feedback loops, avoiding a build-up of broken code as the production date nears.
    
3. Supports CI/CD Pipelines: Continuous Integration/Continuous Deployment (CI/CD) relies on automated tests, including regression tests, to ensure new code integrations are continuously tested. This not only helps find defects but also identifies optimization opportunities, such as UX improvements.
    
4. Detects Visual Bugs: Regression testing isn’t just about functionality; visual regression testing is crucial for spotting visual bugs caused by code changes. Automated regression tests can quickly identify issues like non-clickable buttons or misaligned images across various devices and browsers.
    
5. Ensures Quality with Frequent Modifications: For products that undergo frequent changes, regression testing acts as a quality filter. It ensures that each modification improves the product without introducing new issues.
    
6. Reduces Manual Testing Efforts: Automated regression tests significantly cut down the time and effort needed for manual testing. This efficiency allows QA teams to focus on more complex testing scenarios and other critical tasks.
    
7. Improves Test Coverage: Regularly running regression tests increases test coverage, ensuring that more parts of the application are tested over time. This comprehensive approach helps in maintaining overall software quality.
    
8. Supports Compliance and Standards: Regular regression testing ensures that the application adheres to industry standards and compliance requirements, which is essential for maintaining the integrity and security of the product.

Read More: Latest Innovation in the “Boring” Regression Testing Space

When is Regression Testing Done?

Typically, regression testing is applied under these circumstances:

• A new requirement is added to an existing feature
• A new feature or functionality is added
• The codebase is fixed to solve defects
• The source code is optimized to improve performance
• Patch fixes are added
• A new version of the software is released
• When changes to the User Interface are made
• Changes in configuration
• A new third-party system is integrated with the current system

All of these occasions involve a restructuring or adjustment of the current code, which may result in unexpected behaviors, hence the need for regression testing.

Regression testing the ideal candidate for automation testing due to its repetitive nature, with up to 65% of respondents of the State of Software Quality Report 2024 reporting that they have applied automation to their regression testing activities. To automate regression testing, it is common to leverage a regression testing tool to assist with the coding part as well as test case management, planning, and reporting.

→ Download the State of Quality Report 2024 to get the latest industry insights

How To Do Regression Testing?

Generally, a good rule of thumb is running checks on critical capabilities:

• Features that makes up core business flows
• Frequently used features

With test driven development, each new feature should come out with its own set of tests. For business instances like regression testing, test cases could be readily available for engineers or business analysts to pick out and run on-demand. However, there are always several crucial steps that should be followed.
 

1. Detect source code changes

Identifying the impact and risk of the latest code change is key to building a solid regression test. Conduct code review sessions to identify the components or modules that were changed, as well as their impacts on the existing features. This can be achieved by leveraging a version control system such as Git to compare the differences between the old and new code.

2. Prioritize impacted areas and test cases

After that, QA teams discuss which changes should be extensively tested and which could bare with adequate testing. Modifications that have an impact on core features, or those that significantly alter how the application works, should always be the top priority. 

Defining priorities heightens in importance when the size of the codebase is bigger. The number of tests and time they take to complete could take up to months or an entire sprint. When talking the manual vs. automation testing narrative, regression testing is always the top candidate. 

Given its repetitive nature, teams and companies have standardized the process with automation testing. Whether they’re functional, performance or security checks, this exhaustive list of automation tools shows you the vendor and open source options you have for different testing purposes.

3. Determine Entry Point and Exit Point

Once the team agrees on which changes should be examined, they can select the tests that need to be performed. Generally, testing teams have a range of test suites ready to be executed, but they only have to execute only the relevant ones in each regression testing session. 

Essentially in this step the team formulates a step-by-step plan and prepares the right testing system to perform regression testing. It is necessary to also discard obsolete test cases or test suites for effective test management in the future. 

4. Categorize regression test cases

In this step, we deep-dive into the plan formulated in step 3 and categorize them by various factors. A few common test categorization criteria includes:

• Manual vs automated regression tests: For ad-hoc or non-repetitive test cases, manual testing and human evaluation still make the most sense. Anything that involves the same series of test steps, over and over again, should be automated.
• Critical vs non-critical features: evaluate test cases based on urgency and significance and assign them a value of importance (high, medium, low). Other factors can also be brought into consideration based on business requirements.
• Testing types: each testing type calls for different setup, tools, and environment, so classifying test cases by type (for example functional/non-functional tests) can give the team better control over the testing activities. For the sake of simplicity, many testing teams have gradually adopted a centralized testing system from which they can conduct a wide range of test types without having to constantly switch between platforms

Read More: 15 Different Types of QA Testing

5. Test Environment Preparation 

Having test environments at hand at all times is important for frequent regression testing. As new code are being developed constantly, environments need to be stable and ready-to-test to not interfere with the planned testing schedule. In additional, poor environment setup can give tests more reason to fail, missed defects and false positive/negatives.

Big question: Leverage cloud environments or physical devices?

Overheads and delays in the release timeline can also result in operational inefficiencies. Setting up physical devices and machines involve engineers working with IT, Ops and finance to suffice the ongoing hardware, software, and maintenance costs. 
 

That’s the problem that cloud testing or on-demand cloud environments solve. Say you’re working with a web application for blogging and lifestyle, chances are you wouldn’t need upfront investment in physical hardware like a complex game application would. 
 

Indeed, coverage on different browsers and operating systems is still necessary, but cloud environments would make more sense. Applications with dynamic loads would benefit from the scalability advantage of being able to scale cloud resources up or down.

Read more: Explore Katalon TestCloud | Cloud-based Test Execution Environment.
 

Physical devices won’t be going anywhere either. Applications like games require exact customization on components like graphics cards, processors or memory to test the frame rates, load times and rendering quality. Aside from the default configurations of your physical machine, having a CI pipeline implemented is a standard for most development teams.

6. Schedule And Execute Tests

At this stage, all test cases are ready for execution. Teams can schedule test cases to run based on the test plan. Certain test cases can even be scheduled to run periodically in intervals over the entire development cycle. Time-based test execution allows teams to have greater quality control over the constant changes of their application.

Is time-based execution to test constant changes one of your priorities in testing? If so, learn how to easily manage and set up time-based tests orchestration with TestOps.

7. Measure regression testing success

This stage gives important insights for future test runs. Analytics allows QA managers and other key stakeholders to quantify their testing efficiency and make data-driven decisions. Test reports can reveal weak points in the application for in-time adjustments for the development team.

How To Build A Regression Test Suite?

A regression test suite is a collection of regression test cases grouped by various characteristics like feature, severity, area of impact, or type of tests. The primary goals of a regression test suite are to streamline testing activities, manage test cases efficiently, and prioritize tests faster.

Here are the steps to build a regression test suite:

1. Choose the Right Approach:

• Manual Testing: Involves executing tests manually, which is not ideal for regression testing due to its repetitive nature.
• Automation Testing: Involves using automated scripts or tools, making it more suitable and efficient for regression testing. Automation helps integrate test management activities like planning, organizing, scheduling, and reporting.

2. Assign Tags/Taxonomy for Test Cases:

• Use tags to categorize test cases into functional modules, test case types, priorities, scenarios, and test environments. This helps in organizing and filtering test cases effectively.

3. Have a Naming Convention for Test Suites:

• Establish clear, descriptive naming conventions for test suites. Document these conventions to ensure consistency and easy identification across the team.

Read More: How to build an effective regression test suite?

Top Regression Testing Tools

1. Katalon Platform

Katalon Platform is a comprehensive end-to-end AI-augmented automation testing platform that can take your regression testing to the next level. It is the all-in-one regression testing tool for your website, web services, desktop application, mobile application and even API testing. 

Katalon Platform is a comprehensive test automation and quality management platform for UI-API integration testing. Katalon is dedicated to functional testing. This means you can develop and store web, mobile, API and desktop tests for regression testing. 

Here's a quick demo of how Katalon works:

Thanks to its Record-and-Playback features, any team member can easily capture test objects and record actions that simulate real users’ activity. This sequence can be re-executed in regression testing sessions, saving tremendous time compared to manual testing.

Katalon Platform also supports running scripts on a wide range of devices, browsers, and environments, allowing QA teams to perform a lot of testing activities in just 1 place instead of having to spend time configuring environments and constantly switching tools.

After executing tests, Katalon Platform enables teams to review test results with the comprehensive and customizable test reports in LOG, HTML, CSV, and PDF formats before forwarding them as email attachments. There is a debugging mode for testers to conduct a root cause analysis for a specific failed case. 

The platform integrates seamlessly into your CI/CD pipeline thanks to its diverse integration ecosystem. With its free forever version, Katalon Platform has nearly all of the features your team needs to start testing and bring value at no cost. If you are already testing on a framework, you can also migrate to Katalon Studio without losing any progress.

Not just that, Katalon Platform also comes with many exciting AI features:

• StudioAssist: Leverages ChatGPT to autonomously generate test scripts from a plain language input and quickly explains test scripts for all stakeholders to understand. Learn more about StudioAssist in Katalon.
• Manual test case generator: Integrates with JIRA, reads the ticket’s description, extracts relevant information about software testing requirements, and outputs a set of comprehensive manual test cases tailored to the described test scenario.
• SmartWait: Automatically waits until all necessary elements are present on screen before continuing with the test.
• Self-healing: Automatically fixes broken element locators and uses those new locators in following test runs, reducing maintenance overhead.

2. Selenium

Selenium is highly regarded by developers for its flexibility in regression testing and web application testing. It supports all major browsers, including Chrome, Safari, and Firefox, and can be run on the three primary operating systems: macOS, Windows, and Linux.

By automating tests, Selenium reduces the time and effort needed for manual testing, offering an intuitive interface for creating automated tests. It allows testers to use scripting languages such as Java, C#, Ruby, and Python to interact with the web application being tested. Selenium offers a comprehensive set of testing functions designed specifically for web testing, including:

Selenium Grid: This is a distributed test execution platform that enables parallel testing across multiple machines, significantly reducing test execution time. Selenium Grid comprises a hub and nodes, where the hub coordinates test execution and distributes tests to the nodes, which can be various operating systems and browsers.

Selenium IDE: An open-source record-and-playback tool, Selenium IDE helps develop and execute web application test cases. As a Firefox plugin, it allows users to record, edit, and debug tests. It also supports exporting tests in formats such as JUnit, C#, and Java for integration with other testing frameworks.

Selenium WebDriver: A component of the Selenium suite, WebDriver controls web browser behavior, simulating user actions like clicking links, filling out forms, and uploading files.

The effectiveness of Selenium is closely linked to the testers' coding skills. Those with strong coding abilities can leverage the full potential of Selenium, while less experienced QA teams may find it challenging to fully utilize its capabilities.

Read More: Katalon vs Selenium: A Detailed Comparison

Selenium is a proper solution for large-scale quality assurance teams with advanced testers having expertise and experience. However, its steep learning curve usually is a challenge for small and mid-size teams. Moreover, automation testing scripts written with Selenium have to be continuously revised as code changes occur, which is time-consuming.

3. Watir

Watir, which stands for Web Application Testing in Ruby, is a powerful open-source library that uses the Ruby programming language to automate web application testing. Unlike some other tools, Watir performs testing by directly interacting with web browsers, so it doesn’t require an external server. This makes it easier to set up and run tests.

One of Watir's strengths is its user-friendly interface. Its simple and clear syntax allows users to write test scripts without needing to spend a lot of time reading through complicated documentation. This makes it a good choice for both beginners and experienced testers.

For regression testing, Watir is especially useful. It can automate repetitive test cases to check if recent changes in the code have broken any existing functionality. By simulating user actions like clicking buttons, filling out forms, and navigating web pages, Watir helps ensure that the application continues to work correctly after updates. This helps quickly identify and fix bugs, keeping the application stable and reliable.

Watir can also be integrated with various testing frameworks and tools, such as RSpec and Cucumber to enhance its capabilities. This means teams can use Watir in combination with other tools to create a comprehensive testing solution tailored to their needs.

The tool supports multi browsers and operating systems, and WATIR is equipped with the Attach Method, ensuring that when a linked domain window is opened, the original application window will remain connected. Another interesting feature of Watir is its capability to support diverse user interaction capabilities for web testing, such as clicking links, filling out forms, and validating texts.

4. IBM Rational Functional Tester

Rational Functional Tester (RFT) is an advanced automated testing tool developed by IBM, designed to support a wide range of applications and environments. It is particularly well-suited for regression testing, providing robust features that help ensure the continued functionality and performance of software applications after changes have been made. 

RFT supports various programming languages such as Java and VB.NET, giving testers the flexibility to choose the language they are most comfortable with. IBM Rational Functional Tester features a natural language script editor and rendered screenshots for easy test visualization and editing, plus ScriptAssure technology that allows testers to automate tests that are resilient to frequent UI changes.
 

One of RFT's standout features is its powerful scripting capabilities. Using its ScriptAssure technology, RFT can automatically adapt to changes in the user interface, which reduces the need for frequent script maintenance. This is particularly useful for regression testing, where tests must be repeatedly executed as the application evolves. RFT's ability to maintain and adapt test scripts ensures that tests remain reliable and effective over time.
 

RFT also integrates seamlessly with IBM's broader Rational suite of software development tools, including Rational Quality Manager and Rational Test Workbench. This integration facilitates comprehensive test management and execution, as well as detailed reporting and analysis. Such integration supports a streamlined workflow for teams using an Agile or DevOps approach, ensuring that regression tests are efficiently incorporated into the continuous integration and continuous delivery (CI/CD) pipeline.
 

Additionally, it provides a recorder of user actions, multiple customization options, script maintenance capabilities, and the ability to share functional tests with other team members and run them on hybrid environments.

5. Apache JMeter

Apache JMeter is an open-source Java application for testing load, performance, and functional behavior of web applications. It has been expanded to include testing other functions, such as the efficiency and concurrent user request handling of a server.

JMeter's graphical interface, which is based on the Swing graphical API, is simple to use and can be run on any environment that supports a Java virtual machine, including Windows, Linux, and Mac. It is a great tool for functional performance and regression testing on different technologies.

Regression Testing Techniques

Regression testing has three most prominent implementation methods, including retesting all, regression test selection, and test case prioritization.

1. Retest All

In this technique, regression testing is applied to all existing test suites. It is easy to see that although it is the safest way to ensure all bugs are detected and resolved, this method requires substantial time and resources. 

That is why the complete regression approach fits better in certain contexts. For example, only consider complete regression testing when an application-wide update occurs, such as when the application is adjusted for a new platform or language, or when the operating system gets a major update.

Another suitable use case for complete regression testing (or complete retest) is for small-sized applications. As the number of test cases to be executed is relatively low, QA teams can execute all of them for maximum coverage.

2. Regression Test Selection

With this approach, QA teams may select the relevant parts that can be affected by the changes and perform regression testing on these chosen parts only. By picking out the related areas, you can apply limited and relevant test cases to reduce both the time and effort invested in regression testing.

This approach is suitable for more complex or large-scale applications, whose number of test scripts to be executed is higher.

3. Test Case Prioritization

This approach is essentially prioritizing test cases that must be included and performed first in the regression testing process. These test cases should be prioritized based on several criteria: 

• Failure rate
• Business impact
• Gradually used functionalities
• Test cases to check the functionality of new features 
• Customer-centric features
• Security-related features

There may be many other aspects to consider depending on the specifics of your business and organizations. It is important to understand how business requirements translates into the features of your application for better decision making.

4. Corrective Regression Testing

Corrective regression testing is simply re-running all current test cases when no code change has been made, yet. This practice is to double-check on whether the current code functions fine, and whether we can reuse the existing test cases or not. 

If the test results are positive, QA teams can be confident that their test cases are up-to-date. At this stage, testers can start the test planning and prioritization process while the new code is added.

5. Progressive Regression Testing

With progressive regression testing, testers acknowledge that changes to the code may call for changes in the test suites themselves, so they update the test scripts to align with the new requirements. This approach is employed when there is a change that impacts product vision.

Retesting vs Regression Testing

The two terms retesting and regression testing can be confusing for test automation novices. They might sound similar but are in fact entirely different from each other.

Retesting literally means “test again” for a specific reason. Retesting takes place when a defect in the source code is fixed or when a particular test case fails in the final execution and needs to be re-run. It is done to confirm that the defect has actually been fixed and no new bug surfaces from it. 

Regression testing is performed to find out whether the updates or changes had caused new defects in the existing functions. This step would ensure the unification of the software.

In a typical software development pipeline, retesting is performed before regression testing practices. Retesting solely focuses on the failed test cases while regression testing is applied to those that have passed, in order to check for unexpected new bugs. Another important note is that retesting includes error verifications, in contrast to regression testing, which includes error localization.

Moreover, automation is a crucial feature in regression testing, allowing you to make the most of your test case capabilities. Additionally, regression testing eliminates all underlying side effects caused by code changes in the most cost-effective way possible.

Agile Regression Testing

With the Agile development approach, teams can gain numerous benefits and values, such as accelerated time-to-market, ROI, customer support, and product improvements. However, this comes with a significant challenge of balancing between sprint development and iterative testing to avoid conflicts as the product matures.

Agile implementation of regression testing plays a key role in aligning the existing and updated functionalities, avoiding all possible rework in the future. Agile regression testing ensures the business functions are stable and sustainable.

On another note, regression testing helps developers to focus their efforts on building new functionalities for the application rather than keep on returning to check for defects in the old features. Applying regression testing reveals the unexpected risks in software builds, helping developers to respond more quickly and efficiently.

Conclusion

Regression testing is key to improving the overall quality of the product and user experience. The right regression testing tools can significantly identify all surfaced defects and eliminate them early in the pipeline. 

In addition, regression testing in Agile offers a host of technical and business advantages. Therefore, the more your organization invests in planning and performing regression testing, the more control you will have over the budget, process, and error mitigation of your product.

Up Your Regression Testing Game, Today