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Regression testing is one of the most important testing types in any software development project. At a very high level, the goal is to confirm that new developments did not introduce bugs or defects in previously working areas.

In my experience working with various projects in different business domains, I’ve learned that each team has its own processes for performing software regression testing. However, there are some common points that all successful testing projects share.

This guide equips you with the knowledge to master regression testing. It explores the arsenal of powerful regression testing tools to streamline the process and ensure a smooth development workflow. I’ll share the lessons I learned along the way.

What is Regression Testing in Software Development?

The emergence of new defects and/or re-emergence of issues is relatively normal as software is updated, changed, or reused on a modified target.

regression testing in software development screenshot

To ensure these defects are uncovered before the software updates are released into production, the QA team should focus on finding them in time - and this is where regression testing comes in.

Regression testing is a testing type where the software application's functionality of already existing features is confirmed. Regression testing is carried out after every change or update to the code to ensure that the existing functionalities are operating as intended without any revisions or additions. Depending on the project's scope, either manual or automated regression testing might be used.

When Should You Use Regression Testing?

When new features or improvements are added to an existing codebase or application, regression testing is necessary. It guarantees that any added features or updates to a current application function flawlessly and without errors. There is a high likelihood of code incompatibility issues because developers and testers frequently struggle to trace every thread of code. Because of this, running Regression tests on their software (or application) enables them to find bugs earlier and release software with fewer risks.

Whenever a deployment takes more time than anticipated, regression testing might be applied. In this scenario, the tester needs to perform regression tests every day. Additionally, for weekly releases, it is preferable to perform regression testing following functional testing.

Automated Regression Testing

The regression test library expands as the team adds software features. The regression test suite might grow to such a size over time that it becomes impossible to manually run the tests inside the constrained Agile sprint cycles.

Regression testing is best suited for automation testing because it must be repeatable and recurrent. Before each release, you can perform a thorough regression test, and you can develop leaner, quicker feedback test suites to check for regressions following code changes (hotfixes). Discover software testing tools that are particularly effective for regression testing scenarios.

When to Perform Regression Testing

Regression testing is necessary any time new features or improvements are added to an existing codebase or application. It guarantees that any added features or updates to a current application function flawlessly and without errors. There is a high likelihood of code incompatibility issues because developers and testers frequently struggle to trace every thread of code. Because of this, running Regression tests on their software (or application) enables them to find bugs earlier and release software with fewer risks.

Manual regression testing must be done if test automation is not integrated with the build system and/or automated test runs are not scheduled regularly. Then, is it necessary to backtrack every code change? No, is the response.

Regression testing is only needed when a code change affects other parts of the product. One must examine how the altered module interacts with other product modules to pinpoint this.

Most of the time, developers who make changes are aware of the potential effects on other modules and the behavior of the entire product, and they should appropriately request regression testing as necessary.

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Who is Responsible for Regression Testing?

After functional testing is complete, regression testing is carried out to check that all other functionalities are working. It is usually the responsibility of the QA team. New testers who have not tested the feature before, but can execute documented test cases, can also be involved in the regression process. In these cases, the regression test cases should be properly written so even somebody new on the team can follow them. 

Also, testers who may not have executed the functional tests before but have good experience working with the features that need to be tested have a good chance at finding major bugs, if any have been introduced.

How Do You Know When Regression Testing is Done?

You need to find a delicate balance between what you have time and resources to cover as part of the regression testing and the risk the team can assume.

Here are some things the testing team can into account when estimating risk:

  • If a feature is intensively used by the software’s users, it should be given priority in the Regression Testing plan.
  • Technical areas of the product that have proven stable in the past and have been known to generate good test reports are less risky, so the software testers may choose not to include them as part of the Regression Testing.
  • Analyzing previously reported defects from customers or the internal QA team can help identify weaker areas of the app where regression efforts should focus.
  • If bugs have remained open for a long time without being fixed, they have little impact on the users' workflows, and they have found workarounds for them.

Regression Testing Techniques

The most important techniques used when performing regression are: 

  • Complete regression, also known as retest-all
  • Regression test selection
  • Test case prioritization

Complete Regression

Regression testing is used in this method on all active test suites. Although this approach demands a lot of time and resources, it is the safest technique to guarantee that all defects are found and fixed because it has the highest test coverage.

Because of this, there are specific situations when the complete regression testing strategy works better than others, such as when the application is changed for a new platform or language or when the operating system receives a significant update.

Test Selection (or Partial Regression Testing)

This technique involves selecting test cases from the test suite to run again. The selection of test cases is based on the code changes in the module.

Test Case Prioritization 

When using this approach, you may prioritize test cases with the highest priority to be performed first in the regression testing process. These are also good candidates for automated testing. The tests should be prioritized based on their failure rate, business impact, and used functionalities. 

The test cases that relate to real-life scenarios and new functionalities should be given high priority as well.

Regression Testing vs Retesting

As opposed to regression testing, where testers validate that the existing functionality still works, retesting confirms that a bug has been fixed. Retesting revolves around only failed test cases and focuses on verifying whether the outcome of the test case has changed. 

Agile Regression Testing

When working in an agile environment, new features are introduced every sprint, and the regression test suite should always be kept up to date to assure the appropriate operation of all features after the sprint. In Agile environments where code changes are frequent, efficient QA automation tools can be a lifesaver for keeping up with regression testing. The regression suite should continually add test cases matching all the tested and stable features, and test cases that are no longer applicable should be eliminated.

Visual Regression Testing

The regression testing approach is used in visual regression testing as well. However, visual regression testing only checks the software's visual elements. In other words, it ensures that no component of the software's visual interface is broken by code modifications.

A visual regression test verifies what the user would see once the system has been changed by comparing snapshots taken before and after changes. 

Unit Testing vs. Regression Testing

The goal of unit testing is to validate that individual units of code independently work as expected. It's carried out as the code is developed, unit by unit, early in the development cycle. 

In comparison, regression testing is performed later in the development cycle, when there are code updates or bug fixes. Regression testing usually covers the entire application or software.

Sanity Testing vs. Regression Testing

Sanity testing is performed to evaluate whether the software is operating as intended following the addition of a new module or functionality. Sanity testing is a software testing method that assesses a software release's quality quickly to decide whether it qualifies for further testing.

So, sanity testing evaluates the stability of newly added features or code modifications in the current build. Regression testing verifies that all areas affected by functionality changes or code changes are stable.

Takeaways 

The user experience and overall product quality can be significantly enhanced by regression testing.

Regression testing in Agile also has various technical and commercial benefits. The more your company invests in planning and conducting regression testing, the more control you will have over your product's budget, process, and error mitigation.

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By Andreea Draniceanu

Hi there! My name is Andreea, I’m a software test engineer based in Romania. I’ve been in the software industry for over 10 years. Currently my main focus is UI test automation with C#, but I love exploring all QA-related areas 😊