What is regression testing? A complete guide

Regression testing is a critical part of the software development lifecycle. When developers update code or add new functionality to software, regression testing helps to ensure that the new changes haven’t created issues with existing code or broken the software and its functionality in some way.

Regression testing essentially involves rerunning test cases that have already been executed to make sure software works as intended.

According to Martin Fowler, “People also underestimate the time they spend debugging. They underestimate how much time they can spend chasing a long bug. With testing, I know straight away when I added a bug. That lets me fix the bug immediately, before it can crawl off and hide. There are few things more frustrating or time wasting than debugging. Wouldn’t it be a hell of a lot quicker if we just didn’t create the bugs in the first place?”

In this post, you’ll learn what regression testing is, how and when it’s performed, and the different types. We’ll also go over its benefits and drawbacks and some best practices.

What is regression testing?

Regression testing is a test that ensures that existing features function properly, even with the addition of new features. It checks whether the new changes and updates caused regressions in the code.

For instance, if you have any developmental changes like refactoring of code, bug fixing or dependency updates, you’ll have to run tests again to ensure that the already working functions are not affected.

It also makes sure that new features don’t break the old ones. This is important because if you have an app that’s growing in size and complexity, even a slight change can have a ripple effect on other existing modules.

Take, for example, a banking application that enables users to transfer funds between accounts, check their account balances, and view their transaction history. Reliability and accuracy are crucial in such a high-risk environment; therefore, an update to the system shouldn’t jeopardize the integrity of the current financial operation.

If the development team updates the funds transfer feature to support international transfers, you’d have to conduct regression testing to make sure that when the new feature is pushed, it doesn’t break the existing applications.

What Causes Re-Emergence of Old Faults?

Numerous factors can cause old faults to re-emerge. These include the following:

• Code changes and refactoring. When developers refactor the code or modify it, whether to optimize performance or to add new features, it can unintentionally introduce bugs that had been previously fixed.
• Inadequate testing. If critical tests are skipped or if testing is not done thoroughly, old faults might go undetected. A lack of automated tests to verify fixed bugs and insufficient test coverage can also allow faults to return unnoticed.
• Updates to dependencies. Software applications often rely on third-party APIs, libraries, and frameworks. If these dependencies are updated, it can affect the existing functionality and reintroduce an old bug.
• Merging and version control conflicts. Merging code from different branches can result in conflicts. If an old bug was fixed in one branch but not reflected in the other, then merging can reintroduce an old bug if the fix was overwritten.
• Configuration drift. Any slight change in the configuration between the development, testing, staging, and production environments may recreate previously fixed bugs.

Regression testing in agile is typically continuous and automated to allow development teams to stay focused on innovating with new features and releases

Regression testing in Agile

In the agile methodology, each sprint involves iterative changes in software that may cause problems with existing functionality. As a result, regression testing is critical to the agile process.

It serves as a safety net to ensure that incremental changes do not disrupt previously tested behaviour, a factor crucial for maintaining velocity without compromising quality. Quality assurance (QA) teams should ideally develop test scripts alongside each sprint to ensure that regression testing is executed in a timely way.

Regression testing in agile is typically continuous and automated to allow development teams to stay focused on innovating with new features and releases.

When using CI/CDs, automated regression suites run on each commit, pull request, and pipeline phase to ensure that defects are identified early enough before being propagated through the staging or production environments.

By embedding regression tests into the agile process, software teams can reduce the risk of defects and minimize the time required for developers to fix them.

Why should you perform regression testing?

Here are the reasons regression testing is essential.

1. To ensure new changes don’t break existing functionality. Any new functionality, fix, refactor or dependency upgrade may otherwise impact working functionality. The regression test confirms that the current behaviour continues as desired following the modifications.
2. To identify re-emerging bugs before they reach the users. Bugs that were previously corrected may recur due to a merge, logic rewrites, or changes to the environment. Regression tests identify these returning defects before failing users.
3. To facilitate rapid releases in agile. The high number of code commits, continuous integration, and rapid delivery cycles increases the likelihood of regression. Regression testing ensures that quality isn’t compromised by speed.
4. To retain user confidence and safeguard business-critical processes. Users expect consistency. Interrupting core flows, payments, authentication, dashboards, and transactions may destroy reputation and revenue. Regression testing ensures high-value functionality.

When is regression testing performed?

It’s good to perform regression testing at several points in the software delivery lifecycle:

When new functionality is added

Developers adding new code to a software product aren’t always fully concentrated on its compatibility with existing code. Regression testing can help identify any possible issues early in the development process.

When changes to existing functionality are made

At times, developers make changes to existing code that add or eliminate certain features. When this happens, regression testing can determine whether the changes have had any adverse impact on overall functionality.

Software is newly integrated with other products

When developers enable a piece of software to integrate with other applications or technologies, there’s a possibility that changes in the code could break or compromise existing integrations.

Software is updated

When software is optimized to improve performance, fixed to solve defects, or when patches are added, regression testing can help to make sure that the improvements haven’t created new issues.

Types of regression testing

There are different types of regression tests. Each type has the same goal of identifying bugs and issues but with variations in approach.

1.Complete or full regression tests

These involve all or most existing test suites and may cover much or all of the software’s functionality. Complete regression tests are ideal for establishing the software’s stability and ensuring that it meets project requirements.

While complete regression testing is the easiest way to resolve defects, it’s also more time-consuming, resource-consuming, and costly. This is why it’s typically reserved for scenarios when an application undergoes a major update or when it’s adjusted for a new language or platform.

2. Partial regression tests

Partial regression tests are performed on the part of a software product that has been modified and on adjacent modules that may have been affected. Testing teams can use certain approaches to make sure that a partial regression test produces solid results.

Partial regression is a risk-based approach that balances the risk that an area of code may be affected against the time and resources required for testing. This testing approach is more suitable for large-scale or complex applications, where there are lots of test scripts to execute. It also ensures that new changes don’t affect the existing features.

3. Unit regression tests

Unit regression tests are performed on discrete units or modules isolated from dependencies to ensure the functionality of the unit still works. A unit can refer to an object, module, method, class, function, or even a line of code. These tests help find bugs in the initial software development stages, which, in turn, helps save time and money down the line.

4. Corrective regression testing

This kind of regression testing involves re-running all the test cases before any changes are made to the code. This tests the app’s overall functionality and determines if existing test cases can be reused.

Progressive regression testing helps determine if changes to the code call for modifications or additions in the test suite

5. Progressive regression testing

Progressive regression testing helps determine if changes to the code call for modifications or additions in the test suite. If any changes are needed, the test scripts are updated to reflect those.

How regression testing is performed?

While regression testing can be performed in a variety of ways, there are several essential steps that most testing protocols follow.

1. Identify changes in the source code. Whenever code is modified or optimized, developers or testers must identify the components and modules that were changed, along with any known impact on existing functionality.
2. Prioritize changes and requirements. To make the testing process more efficient, developers should prioritize modifications and test cases based on product requirements, as well as on the modules and functionality that are most commonly affected by changes to the code.
3. Build a regression test suite. A regression suite is a collection of test scenarios that address the various functionalities that are important to the software. Regression suites are typically created from existing functional tests, unit tests, integration tests, and other test cases that have already been executed.
4. Select an approach to testing. While some testers use a manual approach, most development organizations will automate regression testing since regression tests must be repeated many times as software evolves. Automating the process accelerates testing and frees testers to conduct manual exploratory testing.

Automated versus manual regression testing

Automated regression testing is a method that utilises scripts and tools to run test cases repeatedly and without human intervention. This approach enables quick and scalable testing, making it an ideal use case for consistently repeatable testing with each commit or release.

It has ‌high coverage and is cost-effective in the long term , but needs setup in the initial efforts and maintenance. Manual regression testing, however, is what human testers typically do, and it is more suitable for new or rapidly changing features, visual or UX-driven tests, and scenarios that require human judgment.

It is, however, slower, less scalable, and‌ also more prone to human error. Mature teams can utilise both the speed and reliability of automating stable and repetitive regression tests, while manual testing provides exploratory analysis and coverage of new functionality not yet studied, to ensure comprehensive coverage without retarding the release cycle.

Benefits of regression testing

Regression testing can not only improve software quality but reduce the time and cost of fixing defects as well. Other benefits include:

1. Earlier detection of defects during a major update, helping to minimize the impact on customers and users.
2. Allowing developers to focus on new functionality rather than reworking old bugs.
3. Improved user experiences without introducing unintended side effects.
4. Fewer unexpected risks. Regression testing can be an effective part of risk mitigation strategy that helps developers and companies stay on top of changes and problems before they become significant issues.
5. Improved overall system performance. Greater stability in the system ensures the reliability of the core business processes.

Disadvantages of Regression Testing

While regression testing is necessary for maintaining the quality of your software, it has a few drawbacks:

1. It can be quite resource and time-consuming if your testing strategy doesn’t involve automation tools.
2. With that said, you still need infrastructure, testing environments, and tools for automated testing, and a team to support automated or manual testing.
3. You need to conduct regression testing even if you make very small changes in the code, which can create a bottleneck and delay product releases if not managed and executed effectively.
4. As your software evolves, you need to update your regression test cases, which can be pretty challenging if manually testing or using code-heavy script-based automation.
5. Automated regression tests can sometimes produce false positives and negatives.

Regression testing best practices

When it comes to regression testing, it’s important to ensure adequate test coverage without overburdening the testing team. The following best practices can help you do just that:

1. Make sure to run the regression test suite regularly, especially when there are new changes. This will ensure you catch new issues early and fix them before they become bigger.
2. Always select test cases that cover the software’s most relevant and critical features. It’s also a good idea to prioritize them based on the frequency of their execution and impact on the application. This approach will ensure that you always test the most critical functions.
3. Automate regression tests as much as possible to reduce the resources, time, and effort needed for testing while increasing test coverage and improving the accuracy and consistency of test results. Automation can also allow for faster feedback loops.
4. Make sure you update your regression test suite and add new test cases regularly to reflect the changes made to the software. This will make sure that you don’t miss any issues during testing.
5. Keep track of all the bugs found during testing and report them to ensure that developers address them on time.
6. Don’t forget to document your testing process to ensure consistency. Make sure you include the testing frequency and the test cases so that you can easily replicate the process.

Tricentis tools for regression testing

Tools for regression testing streamline the process of re-running tests, making it faster and more efficient to catch issues introduced by code changes. By automating repetitive tasks, these tools help ensure software stability, reduce human error, and improve productivity, allowing teams to focus on enhancing quality and accelerating releases.

With the industry’s #1 continuous testing platform, Tricentis is reinventing software testing for DevOps. Providing agile test management and advanced test automation that is optimized to support 160+ technologies, Tricentis transforms testing from a roadblock to a catalyst for innovation.

Solutions provided by Tricentis for regression testing include:

Tricentis Tosca

Tricentis Tosca accelerates testing with an automated, no-code, AI-based approach to end-to-end test automation. Tosca breaks through the barriers created by legacy and conventional functional testing automation methods.

With an innovative risk-based and model-based approach to test automation, Tosca simplifies end-to-end regression testing for 160+ technologies.

Tricentis Elastic Execution Grid

Part of the Tosca solution, Tricentis’ modern cloud-native Elastic Execution Grid delivers next-gen test execution and streamlines regression testing by distributing automated test sets across multiple virtual machines, computers within a network, in a user’s private cloud, or in the Tricentis Cloud environment for zero-footprint execution.

Testers can specify which tests should be run in different contexts by configuring available agents, while this Tricentis solution automates load balancing and parallel execution to achieve highly scalable and optimal distribution of test sets.

The Tricentis platform also offers a suite of additional testing solutions and QA testing tools that include data integrity tools, Jira testing tools, performance testing tools, software test automation tools, and tools for ServiceNow, Snowflake, SAP, Oracle, and Salesforce test automation.

By retesting the software after updates or enhancements, regression testing makes sure that new changes don’t reintroduce old bugs or disrupt existing functionality

Conclusion

Regression testing is essential for improving your product’s quality and ensuring its stability and integrity as it evolves. By retesting the software after updates or enhancements, regression testing makes sure that new changes don’t reintroduce old bugs or disrupt existing functionality.

With Tricentis solutions for regression testing, you can deliver high-quality and reliable products that meet your users’ needs and maintain their trust. Eliminate regression bottlenecks, start your free trial now and keep every release fast and reliable with Tricentis.