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What is Regression Testing? Definition, Tools & How to Get Started

What is regression testing?

Regression testing is a software testing practice that ensures an application still functions as expected after any code changes, updates, or improvements.

Regression testing is responsible for the overall stability and functionality of the existing features. Whenever a new modification is added to the code, regression testing is applied to guarantee that after each update, the system stays sustainable under continuous improvements.

Changes in the code may involve dependencies, defects, or malfunctions. Regression testing targets to mitigate these risks, so that the previously developed and tested code remains operational after new changes.

Generally, an application goes through multiple tests before the changes are integrated into the main development branch. Regression testing is the final step, as it verifies the product behaviors as a whole.

When to apply regression testing

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
  • Changes in configuration

Why is regression testing important?

Test automation is a necessary element in software development practices. Similarly, automated regression testing is also considered a critical puzzle piece.

With a rapid regression testing process, product teams can receive more informative feedback and respond instantly. Regression testing detects new bugs early in the deployment cycle so that businesses do not have to invest in costs and maintenance efforts to resolve the built-up defects. Sometimes a seemingly mild modification might cause a domino effect on the product’s key functions. That’s why developers and testers must not leave any alteration, even the smallest, goes out of their control scope.

Functional tests only inspects behaviors of the new features and capabilities, yet dismiss how compatible they are with the existing ones. Therefore, without regression testing, it is more difficult and time-consuming to investigate the root cause and the architecture of the product.

In other words, if your product undergoes frequent modification, regression testing will be the filter that ensures quality as the product is improved.

Regression Testing chart

How to perform regression testing

Regression testing practices vary among organizations. However, there are a few basic steps:

Perform Regression Testing

  • Detect Changes in the Source Code

Detect the modification and optimization in the source code; then identify the components or modules that were changed, as well as their impacts on the existing features.

  • Prioritize Those Changes and Product Requirements

Next, prioritize these modifications and product requirements to streamline the testing process with the corresponding test cases and testing tools.

  • Determine Entry Point and Entry Criteria

Ensure whether your application meets the preset eligibility before the regression test execution.

  • Determine Exit Point

Determine an exit or final point for the required eligibility or minimum conditions set in step three.

  • Schedule Tests

Finally, identify all test components and schedule the appropriate time to execute.

Regression testing techniques

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

Complete Regression

In this technique, regression testing is applied to all existing test suites. 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, when the application is adjusted for a new platform or language, or when the operating system gets a major update.

Regression Test Selection

You 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.

*Test Case Prioritization *

You may choose to prioritize test cases that must be included and performed first in the regression testing process. These test cases should be prioritized based on these criteria: failure rate, business impact, and gradually used functionalities.

The test cases that relate to customer-facing aspects and newly added functionalities are of high priority as well.

Best regression testing tools

Katalon Studio

Katalon Continuous Testing Tools

Katalon Studio is an end-to-end automation solution that supports functional and regression testing, transforming these processes into easy and simple tasks for testers.

Katalon Studio provides an all-in-one regression testing tool for your website, web services, and mobile application. The tool also supports running scripts on multiple devices, browsers, and environments.

In detail, you can review test results with the comprehensive and customizable test reports in LOG, HTML, CSV, PDF formats, and forward them as email attachments.

Download Katalon Studio


Selenium Continuous Testing Tools

Selenium offers a set of features used to automate web applications. It remains among the top tools for browser-based and cross-platform regression testing. Selenium supports automated test scripts that cycle through data sets and data-driven tests. This is a proper solution for large-scale quality assurance teams with advanced testers. However, its steep learning curve becomes a hindrance for small and mid-size teams.


Watir logo

Watir, or Web Application Testing in Ruby, is an open-source library using the Ruby programming language. It supports writing tests that are easy to read and maintain on a lightweight and flexible user interface.

Watir supports diverse user interaction capabilities for website testing, such as clicking links, filling out forms, and validating texts on a variety of browsers.

IBM Rational Functional Tester

RFT logo

Rational Functional Tester, or RFT, is a tool for software test automation from IBM. RFT can be used for a wide range of software testing types, including functional, regression, GUI, and data-driven testing, and applications (web-based, .Net, Java, Siebel, SAP), and more.

Apache JMeter

Apache JMeter

Apache JMeter is an open-source test automation software used to load functional test behaviors and measure test performance. It is capable of many testing features, including support for load and performance tests on many different applications, server or protocol, as well as providing a whole regression test suite for the end users.

View more tools here.

Differences Between Re-testing and Regression Testing

The two terms re-testing and regression testing can be confusing for automation novices. They might sound similar, but are entirely different from each other.

Re-testing literally means “test again” for a specific reason. Re-testing 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.

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, re-testing is performed before regression testing practices. Re-testing 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 re-testing includes error verifications, in contrast to regression testing.

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.

Regression Testing in Agile

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.


Regression testing is key to improve 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.

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