What Is Regression Testing? Definition, Techniques, and Tools

Regression testing is a process that maintains the quality of a software product while it undergoes frequent modifications.

Last Updated: October 6, 2022

Regression testing is defined as a type of software testing technique that re-runs functional and non-functional tests to ensure that a software application works as intended after any code changes, updates, revisions, improvements, or optimizations. This article explains regression testing in detail, its fundamental techniques, and the top five regression testing tools.

What Is Regression Testing?

Regression testing refers to a software testing technique that re-runs non-functional and functional tests to ensure that a software application works as intended after any code changes, updates, revisions, improvements, or optimizations. It is an integral part of the software development cycle as it allows developers to detect unexpected faults in an application that may arise due to tweaks, enhancements, or extending of the existing codebase.

Regression testing provides overall stability to the software application by keeping a check on the functionality of the existing features. It is an inevitable step after every new code modification, ensuring the system can sustain and withstand frequent improvements.

Technically, code change may cause a change in dependencies, thereby leading to defects or malfunctions in the software. Regression testing is put in place to minimize such risks. It enables professionals to verify whether the previously developed and tested code stays operational when new features or code changes are introduced.

Typically, any software application goes through a series of tests before the changes become a part of the development package. Out of those multiple tests, regression testing constitutes the last step and is responsible for adjudicating the product’s behavior in its entirety.

Moreover, the rapid regression testing process allows product development to receive informative feedback, which can be responded to immediately and allows instant modification of the software code. With regression testing, one can detect bugs in the early stages of the software development cycle (e.g., Agile software development), thereby saving businesses from investing in maintenance efforts in terms of both the time and cost necessary for resolving built-up defects.

It has been observed that the slightest code modification can cause a domino effect that can alter a product’s primary functionalities. Thus, regression testing plays a key role in investigating the product’s architecture, which is crucial to determine the root cause of both product success and failure.

Let’s consider a simple example of a software company that develops video conferencing platforms. The company must ensure that the first version of the software platform or product includes the basic core features. While releasing its first build, the company undertakes regression testing that comprises 1,000 test cases. Such a practice validates whether the platform has fundamental or freemium conferencing functionalities. The product is ready to roll out into the market after passing the tests successfully.

As the product’s first version gains popularity in the video conferencing platform space, the demand for additional functionalities grows amongst clients and customers. Thus, business teams understand client and customer sentiments and bring in the requirement for new features that one can release in the premium versions of the software. The product development team follows the instructions and adds new features to the existing product.

On adding new functionality, regression testing again becomes essential. Here, a few hundred (say 100) test cases are run to verify the working of newly-added features. However, it is crucial to consider that the 1,000 test cases that were conducted need to be re-run just to ensure that the freemium version’s critical functions aren’t affected, impacted, or broken due to the addition of newer ones.

In a nutshell, this is how regression testing operates. Although it is tedious, it effectively identifies critical bugs or issues that occasionally occur. Generally, regression testing is used in the following circumstances:

  • A new requirement is added to the existing product feature
  • A whole new functionality or feature is added to the product
  • Optimized codebase to improve performance
  • Adding patch fixes
  • Configuration changes

How to perform regression testing

Regression testing strategies vary for every organization. However, some of the fundamental steps followed by most include:

Regression Testing Process

Regression Testing Process

Step I: Identify changes in source code

In this step, the source code changes (modifications & optimizations are identified). It is further followed by detecting changed components and the impact all this had on the existing essential features of the product.

Step II: Prioritize identified changes & product requirements

In the next step, all identified product requirements and code modifications are prioritized by aligning the test process with requisite tools and test cases.

Step III: Select test cases to re-run

Next, the test cases to re-run are selected based on the source code-modified module. Here, one is not required to test the entire test suite. Post-test case selection, test cases are categorized into reusable and obsolete test cases, wherein the reusable ones are shortlisted for regression testing. In contrast, the obsolete ones are not used for future testing cycles.

Step IV: Consider test scenarios to determine test case execution time

Test case variables, such as test data preparation, regression test designs, etc., are evaluated to determine how they impact the test case execution time.

Step V: Categorize automated & manual test cases

This step separates the test cases into automated and manual ones. Automated test cases are faster than manual cases managed by humans. Also, one can reuse the test code multiple times in the automated scenario. Hence, categorizing test cases is a crucial step in regression testing.

Step VI: Prioritize test cases

In this step, the collected test cases are ranked based on their significance (high, medium, and low). On evaluation, urgent test cases are given priority, followed by those of medium and low importance. Essentially, priorities are assigned based on the product’s utility and user participation.

Priorities are assigned based on the following criteria:

  • Priority 0: Important test cases that cover all essential features
  • Priority 1: Features that do not fall under the essential category but have a certain importance
  • Priority 2: Test cases that deal with technical complexities

Step VII: Schedule & execute test cases

In the final step, each test case is individually conducted at an appropriate, scheduled time to verify if the product performs as expected. Here, automated or manual testing can be employed depending on the needs and requirements. Automated tools such as Selenium, IBM Rational Functional Tester, Watir, etc., can help faster test case execution.

See More: What Is a Neural Network? Definition, Working, Types, and Applications in 2022

Regression Testing Techniques

Regression testing is realized by employing four basic implementation techniques: retesting everything, selection of regression tests, prioritization of test cases, and the hybrid strategy.

Regression Testing Techniques

Regression Testing Techniques

Let’s understand each technique in detail:

1. Retest everything

This method applies regression testing across every existing test suite when multiple updates or changes are made to a software application’s primary or root code. This technique is key to identifying and resolving all bugs; however, it is time-consuming and resource-intensive. Hence, such an approach is implemented by considering contexts. For example, complete regression is the preferred choice when an application is moved to a new platform or when there’s an update to fix a major bug in the O.S.

2. Selection of regression tests

In this technique, you have the choice to select the parts on which one can perform regression testing. The relevant parts are chosen based on the magnitude of the impact the changes can have on the application. Moreover, with such an approach, limited test cases are applied to related areas, reducing the effort, resources, and time required for regression testing.

3. Prioritization of test cases

This regression testing technique allows you to choose the test cases that you should give the first priority in the testing process. The test cases are selected based on several factors, such as most commonly used functionalities, feature failure rate, and business impact of certain features. More so, newly-incorporated functionalities and customer-centric features are regarded as the highest priority test cases.

4. Hybrid strategy

This regression testing approach combines the principles of the previous two techniques: test case prioritization and regression test selection. The hybrid technique is beneficial in several cases as the need to pick up all test cases simultaneously is nullified. Instead, you can run test cases based on the requirement and need here. Such a dynamic style saves effort and time while testing applications.

Now we’ll look at the different regression testing types where the above techniques are applied:

  • Corrective regression testing: Corrective testing is used in scenarios where changes or updates have not been made to the source code. Here, as you intend to validate the functioning of the current features, you can re-use existing test cases.
  • Progressive regression testing: Progressive testing is applied when new system components are introduced that require new testing environments or test cases to be developed. This type helps determine whether the updates or changes affect the existing components.
  • Selective regression testing: Selective testing is applied when only select components must be retested, thereby saving the time and resources necessary for the entire system.
  • Partial regression testing: When changes are made to the application’s existing source code, partial testing is employed to make sure that the new programming line has not influenced or disrupted the application’s overall performance.
  • Complete regression testing: The whole testing type is applied to the entire software structure when multiple updates are introduced into the root code. This exhaustive testing category is typically used before a product launch.
  • Retest-all regression testing: This regression testing type is a comprehensive approach that re-executes every test scenario by using all the previous test cases compared to the last testing outcomes. It also ensures that new source code modifications do not cause problems in the overall application functionality.
  • Unit regression testing: In unit testing, units of code are isolated and tested without affecting their dependencies, thereby promoting independent code testing.

See More: Linear Regression vs. Logistic Regression: Understanding 13 Key Differences

Top 5 Regression Testing Tools

With applications growing in sophistication and complexity, every organization is inclined toward offering a seamless user experience to its target community. As a result, regression testing tools are gaining popularity and are increasingly being employed by various businesses.

According to an August 2022 Global Market Insights (GMI) report, the software testing market accounted for $40 billion in 2021 and is expected to expand at a CAGR of 6% between 2022 and 2030.

Testing tools are key in simplifying, optimizing, and automating the regression testing process. These are the top five regression testing tools that are popular across businesses:

1. Selenium

Selenium is a popular testing tool that provides testing application features. Developers can use the environment to test workflows for their functional, acceptance, and performance aspects. It uses an extensive library of extensions and plugins that allow you to expand the tool’s basic functionality. It seamlessly integrates third-party tools such as SauceLabs, Selenium-Grid, JUnit, etc.

Moreover, Selenium is a language-independent tool, implying that quality assurance professionals need not learn a specific language if they intend to automate their tests through Selenium. Language support goes from C#, Java, Ruby, JavaScript, and PHP to Python. Also, the tool has a more extensive community base, including developers from players such as Google and startups that can guide you wherever necessary. In a nutshell, Selenium offers a comprehensive toolkit for a testing ecosystem.

Pricing: Single user costs $2800. Add extra machines and users with an additional $850.

2. Ranorex Studio

Ranorex Studio automates tests for mobile, desktop, and web apps. It is used by leading companies such as IBM, Dell, Cisco, Siemens, Adidas, Lenovo, and others due to its easy-to-use and codeless interface that offers several valuable wizards and IDEs.

The tool allows you to set up tests by using reusable code modules and share object repositories that multiple tests or application components can access. The tool provides data and key-driven testing approaches and can be integrated with other tools such as Git, Jira, and Jenkins for improved performance and advanced testing insights.

Pricing: Runtime License – $980.00 (1 per additional physical or virtual device with one-time purchase), Ranorex Studio License – $3,950.00 (1 Workstation with one-time purchase).

3. Katalon Studio

Katalon Studio is built on the foundations of Selenium. According to a March 2020 report by Gartner Peer Insights, this tool was recognized as the popular customer choice for software test automation tools. The tool is supported on various devices such as macOS, Linux, and Windows. Moreover, it provides testing functionalities to desktop, mobile, and web applications and support for specific APIs.

Katalon Studio also provides additional testing extensions and plugins, along with added recording and spying features. It explores various testing methodologies, such as data and key-driven approaches. Moreover, the tool also has a large customer base, giving users access to a vast software test automation market community.

Pricing: Basic low code Katalon Studio version is available for free. The ‘Studio Enterprise’ version costs $1,899 /license/year, wherein, one license is tied to one user account. The ‘Runtime Engine’ version costs $1,499 /license/year, wherein users can share one license across multiple accounts or machines.

4. TestComplete

TestComplete allows enterprises to automate regression tests using a user-friendly interface. It is a GUI testing tool that uses artificial intelligence to test applications over mobiles, web, and desktops. Moreover, it also provides easy integrations with third-party tools.

Companies such as Cisco and Thomson Reuters rely on this tool for quick identification and bug fixing in software codes. Additionally, the tool allows scheduling regression tests without requiring human intervention.

Pricing: Free trial is available for this tool. The version ‘TestComplete Base’ can be used for $6,595 (desktop + mobile + web), while one can use ‘TestComplete Pro’ for $5,075.

5. Sahi Pro

Sahi Pro is an automated tool for regression testing aimed toward large web applications with minimum maintenance efforts. The tool uses an intelligent accessor mechanism to keep the test script intact despite the UI changes. Moreover, the testing tool offers to log and report features and alternatives to email reports to concerned personnel.

Sahi Pro does not require coding skills to experiment with. Instead, it offers easy-to-use APIs for user access. It uses a DD CSV file for script execution, making it easier to manage.

Pricing: $695/year per user license.

See More: What Is Narrow Artificial Intelligence (AI)? Definition, Challenges, and Best Practices for 2022

Takeaway

Regression testing is vital for improving software product quality and enhancing the end-user experience by ensuring that code changes do not impact the older or existing product functionality. Using appropriate regression testing tools eliminates software defects early in the software deployment cycle.

Thus, businesses investing more in the planning and implementation of regression testing will have better control over the expenses, efforts, resources, and time invested in raising the quality of their software products. 

Did this article help you understand the role of regression testing in the success of a software product? Comment below or let us know on FacebookOpens a new window , TwitterOpens a new window , or LinkedInOpens a new window . We’d love to hear from you!

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Vijay Kanade
Vijay A. Kanade is a computer science graduate with 7+ years of corporate experience in Intellectual Property Research. He is an academician with research interest in multiple research domains. His research work spans from Computer Science, AI, Bio-inspired Algorithms to Neuroscience, Biophysics, Biology, Biochemistry, Theoretical Physics, Electronics, Telecommunication, Bioacoustics, Wireless Technology, Biomedicine, etc. He has published about 30+ research papers in Springer, ACM, IEEE & many other Scopus indexed International Journals & Conferences. Through his research work, he has represented India at top Universities like Massachusetts Institute of Technology (Cambridge, USA), University of California (Santa Barbara, California), National University of Singapore (Singapore), Cambridge University (Cambridge, UK). In addition to this, he is currently serving as an 'IEEE Reviewer' for the IEEE Internet of Things (IoT) Journal.
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