What is Regression Testing?

While the most simplistic definition refers to it as a repetition of tests, regression testing is a type of testing that evaluates a system’s functionality to validate or reject that previously developed and tested software performs successfully after a change is implemented. In essence, regression testing verifies software functionality after it undergoes changes. 

What is regression testing? By definition, the term regression means “the act of going back to a previous place or state; return or reversion.” Using this meaning in the software development field, regression testing is used to assess if software or specific software components have not inadvertently reversed to a previous state. That is, when adding new features to the software, we need to be absolutely sure that the functionality of the previous version works just as reliably and gives us the expected results when entering test values. If we're fixing a bug in the software, we also need to make sure we haven't made the bug elsewhere. The task of regression testing is precisely to make sure that the functionality of the new version works reliably relative to previous versions.

Typically, a regression test is performed each time a change or modification is implemented to identify if there are any issues or defects that should be addressed. Testers re-execute tests in the modified application to make sure the modified code doesn’t disrupt any component that was working correctly in previous versions.

The typical changes that may require a regression test include bug fixes, requirement changes, performance fixes, software enhancements, configuration changes, new features, component substitutions, etc. It is relatively common that when any of these changes are performed there will be new faults, defects, or issues.

How to do Regression Testing?

Regression testing is a necessity where software maintenance is concerned; specifically, if it includes enhancements, error corrections, optimization, or deletion of existing features.

When thinking about ​​what is a regression test, each team needs to understand and validate each stage of the product life cycle. If we do regression testing correctly, we will have fewer errors on the production version of the software product. Often, software developers and testers think that if we don’t change this specific subsystem in the project, then we don’t need to perform regression testing on it. Unfortunately, errors appear in the place where nobody expected them.

To perform a regression test, there are a few, simple steps that must be followed: (1) identify each occurrence in which a modification is made since it must be checked to determine if it affects negatively any of the previous working aspects of the code; (2) prioritize changes and requirements to tackle each one accordingly and identify the appropriate test/use cases for the project; (3) define an entry point and entry criteria for the regression test to ensure the eligibility or set of minimum conditions that should be met prior test work; (4) define an exit or final point to set the eligibility or minimum conditions that must be met before finalizing the test phase; and (5) create a test schedule and identify the initial unit tests for the components that should be completed.

There are two implementation methods for regression testing: full and partial regression.

Full regression testing encompasses all regression test cases. Usually, QA teams perform full regression testing in the final stages of the software development lifecycle or prior to major releases. Full regression testing works well when a project undergoes significant functional and non-functional changes, or when these changes affect the root code. Typically, testing teams revise test suites and select the best test cases that find defects throughout the process. These collections of test cases form the regression test suite, and while it is considered a tedious and time-consuming implementation method, full regression testing is highly effective.

Partial regression testing focuses on testing the features of modified sections of a software system, as well as related areas that may be affected. To yield successful results, testers single out application areas that may be affected by code changes and select only the relevant test cases from the test suite. This implementation approach is valuable for iterative methodologies such as Agile, where teams are pressed for time.

Basically, these two implementation approaches depend on the scope of changes, software development methodology, and the stage of the software process.

Besides the importance of selecting the right implementation method, there are several best practices when performing regression testing:

• Schedule: Maintaining a schedule helps sustain a steady rhythm during the software development lifecycle, thus preventing testing from being  delegated to a secondary role.
• Test management tools:  test management tool that helps testers track all the tests being performed to keep a historical record of performance over time is highly recommended.
• Test prioritization: Categorize tests appropriately to ensure the most relevant tests are being performed ahead of minor ones.
• Refactor tests: Break tests down into small tests to sort and execute with greater ease.
• Risks: Considering the risks and effects specific tests will have on the client or on the project as a whole is helpful to create contingency plans and be prepared for any situation that may arise.
• Exploratory testing: Performing exploratory tests ensures that the software functions as expected.

Importance of Regression Testing and Software Development Lifecycle

Within the Software Development Lifecycle framework, testing is critical. As previously defined, regression testing is considered an extremely valuable coding practice to ensure a system is working properly after any change is implemented. 

The overall goal of regression testing is to easily and effectively detect bugs or defects that are recently created, whether local or remote, or undiscovered which are also known as unmasked. Ideally, the software development lifecycle provides the right framework to perform regression testing as needed and everywhere it is needed, but with several elements in the equation, it can sometimes take a backseat to other types of testing.

Now, regression testing is done in which phase? Is it better to perform regression testing right before deployment of the new version to the production server? Or is it better to do it in the early stages of feature development? Usually, the initial regression testing is performed when we have a beta or alpha version of the software, or in every iteration if using SCRUM methodology.

It’s a real challenge for testers to decide when and where regression tests should be included, so it is important to design and maintain feasible regression tests.

These are the embedded benefits and overall value of conducting regression testing in the software development lifecycle:

• Increase the likelihood of detecting defects or bugs caused by changes introduced in the software.
• Identify any undesired side effects of a new operating environment.
• Upgrade software performance by identifying defects and bugs in the early stages of the process.
• Ensure quality in scenarios where changes are frequently introduced in the software.
• Provide a superior maintenance experience and deliver high-quality software.

How to build the right Regression Testing strategy

An effective regression testing strategy is critical to ensure the success of a software development project. There are key main factors that should be taken into account to design a regression testing strategy:

• Product nature: Based on the type of software product, the relevant regression testing strategy will differ. For example, the approach to test a landing page will be very different from the approach of testing a full-fledged website.
• Product scale: Different approaches to designing a regression testing strategy will be required based on whether it’s a small, medium, or large software project. For example, for a small project, testers may only perform one single round of manual regression testing while a large project may require multiple manual and automated regression testing rounds.
• Testing methods: Select between manual and automated regression testing.
• Testing approach: Identify what approach suits the needs of the project best, whether it is full or partial regression.  The approach chosen should match the project requirements.
• Quality regression testing suite: A quality testing suite may involve functional and non-functional test cases, granted they cover all the features that were modified during a delivery stage of the software development lifecycle process.

With these critical elements in mind, testers can design a comprehensive and valuable strategy that aligns with all aspects of regression testing. A sound regression testing strategy reduces testing time and effort while enhancing product quality to meet or exceed specific client requirements.

Next, we are going to give an overview of regression testing methodologies, test cases, and tools to address how a successful regression testing strategy is built.

Regression Testing methodologies

By performing regression testing, testers select a full or partial collection of already executed test cases which are then re-executed to make sure that existing functionalities work successfully - in essence, these test cases are re-executed to ensure old code still works after changes to the code are implemented. 

A regression test can be manual or automated. Manual regression testing is a basic method of testing every product, proved to be efficient in early stages of the software development lifecycle. The main issue with manual regression is that it is time and resource consuming. On the other hand, automated regression testing is a method that reduces the workload of the testing team by automating tedious and repeatable tasks. It is used more frequently for medium and large projects.

While more are beginning to emerge, there are three principal methodologies or approaches that can be executed to perform a regression test:

• Retest all: This technique involves all tests in an existing test bucket or suite that is to be re-executed to check the integrity of each one. This technique is expensive and labor-intensive as it requires a re-run of all test cases, but it is also a very comprehensive technique as it ensures there are no errors because of modified code.
• Regression test selection: With this technique, only a specific part of the testing suite is re-executed. Naturally, this technique is less expensive than its Retest all peer and it categorizes test cases as reusable or obsolete. Reusable test cases can be reused in subsequent regression cycles, while obsolete test cases can’t be reused in any following cycles.
• Test case prioritization: In this technique, test cases are prioritized based on business impact This means that critical and frequently used functionalities which elevate the test suite’s rate of fault detection are assigned higher priority.  There are two types of prioritization: general and version-specific. In general prioritization, tests cases are categorized based on how beneficial they are for subsequent versions. In version-specific prioritization, tests cases are categorized based on a particular version of the software.

Building the right Regression Test Cases for a system

Effective regression tester must build and select the right regression test cases for a system. There are certain guidelines that should be considered to select the best regression test cases:

• Test cases with frequent defects.
• Test cases with functionalities that are more visible to users.
• Test cases that verify core features.
• Test cases of functionalities that have experienced frequent changes or modifications.
• Test cases of integration.
• Test cases that are particularly complex.
• Test cases of boundary values.
• Test cases that have been successful.
• Test cases that have resulted in failure.

Selecting the best Regression Testing tools

Next, we are going to cover some of the best and most popular regression testing tools:

• Selenium: Top open source regression testing tool used to automate web applications; it is often employed to build powerful, browser-based regression automation suites and tests. While it is not a testing tool per se, Selenium has software tools that allow users to run automated test scripts to cycle through data sets and perform data-driven tests. It offers a cross-environment with support for both operating systems and browsers.
• HP Quick Test Professional (QTP)/Unified Functional Testing (UFT): Tool that provides functional and regression test automation for software applications and environments. It supports keyword and scripting interfaces by using a Visual Basic Scripting language to specify test procedures and manipulate objects and controls of the application being tested.
• SahiPro: Open source automation tool that automates web, web services, desktop, and mobile applications with a single script. It is best used for large web applications that require minimum maintenance efforts.
• AdventNet QEngine: A licensed tool used for regression testing of web applications. It is an extensive, platform independent automation tool that records events and supports playbacks.
• Ranorex: Regression testing software tool for automation used to test desktops, web-based applications, and mobile applications. It supports the development of automated test modules using standard programming languages such as C# and VB.NET.
• TestComplete: SmartBear’sTest Complete is a tool that enables testers to create automated tests for desktop, web, and mobile applications. Tests are recorded, scripted, or manually created with keyword driven operations. It includes a hybrid object recognition engine powered by Artificial Intelligence to detect and test every desktop, web, or mobile application.
• Watir (Web Application Testing In Ruby): Open source library that enables users to automate tests by using the Ruby programming language. It is lightweight and includes top-notch browser interaction capabilities.
• TestingWhiz: Automation solution tool used for regression testing. It supports web testing, mobile testing, cross-browser testing, web services, and database testing. It has a codeless architecture with a fast automation engine.
• IBM Rational Functional Tester (RFT): Tool for automated functional testing and regression testing. It provides automated testing capabilities for functional, regression, GUI, and data-driven testing. It supports applications such as .NET, Java, Siebel, SAP, PowerBuilder, AJAX, Adobe Flex, and more.
• Silk Test: An automated testing tool that is based on the Object Oriented Programming language, which is similar to C++. It supports test script conversion from text to GUI commands and performs regression testing on all machines and nodes.

Continuous Integration and Regression Testing Analysis

Continuous integration enables the automation of release management processes with the purpose of delivering a quick reaction or response. Continuous integration thrives with automation. In a continuous integration framework, there are several tasks that must be carried out to obtain valuable results. 

These tasks include: use a version control system, create uniform build scripts that can be configured to any given machine, configure a continuous integration server to build code, enforce good practices for each small piece of code, extend build scripts to run all unit tests each time the code builds successfully, add end-to-end tests and non-functional requirement tests, address automatic deployments to the QA environment, and monitor QA deployments.

Environments with a continuous integration development framework require that developers and software engineers integrate new or changed code with the main code. This helps reduce the amount of code rework and speeds up the development process. Oftentimes, continuous integration leverages regression testing techniques to select a subset of test suites for modules that render a phase more cost-effective.

Conclusion

Regression testing is successful as part of a comprehensive testing methodology within the Software Development Lifecycle. It must be cost and resource efficient while incorporating a well-designed strategy. Nowadays, regression testing is gaining momentum as an essential aspect of a dynamic, iterative development and deployment software process, and all testers should take advantage of it.

Regardless of the software development lifecycle approach or quality-assurance process testers and organizations use, careful planning and designing are crucial to help prevent projects from exceeding budgets, not meeting schedules or goals, or missing defects or bugs. 
All software development lifecycle processes must include testing. Testing has become a vital and critical element to ensure a software product or application delivers the expected results with a high-quality approach. Regression testing is a powerful step to accomplish these desired results, which is why it is important to include it in any testing strategy.

Svitla Systems is a hub for some of the most talented testers who are at the ready to jump into any project with full commitment and a willingness to display their full range of top-quality skills. Our team of Quality Assurance professionals help reduce the risks of immature software through stringent practices of testing and assessment to ensure the quality of any software product. With strong knowledge of different manual and automation tools, our experts build a customized QA strategy for your business, including all the different forms of testing.

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