What is Regression Testing? A Complete Overview

What is QA regression testing?

Regression testing plays a crucial role in software development as it guarantees the stability and reliability of a system over time. Regression testing becomes essential as software development constantly evolves and undergoes frequent changes and updates. This article will explore regression testing in detail, including its significance, methods, best practices, and how it fits into the broader software development life cycle.

Table of contents

• What is Regression testing?
  • Example of regression testing
• Why is regression testing important?
• Types of regression testing
  • Corrective Regression
  • Retest-all Regression
  • Selective Regression
  • Partial Regression
  • Complete Regression
  • Unit Regression
• How to perform regression testing?
• Challenges and difficulties of Regression testing
• Comparing Regression testing to others
  • Regression Testing vs. Retesting vs. UAT
  • Regression testing vs Smoke testing
• Commonly asked questions on regression testing
• Conclusion

What is regression testing?

Regression testing is an essential part of software quality assurance that involves verifying that modifications to the codebase, such as adding new features, fixing bugs, or updating existing features, do not adversely impact the base functionality of the software. It is not a one-time procedure but rather a series of tests that ensure the continued accuracy and reliability of the application.

Regression testing aims to identify unintended changes, acting as a system-wide test to safeguard against potential disruptions caused by even minor alterations in one part of the system. By re-executing previously cleared test cases against the updated version, this process ensures that recorded bugs do not resurface, maintaining the integrity and stability of the software throughout its development lifecycle.

Example of regression testing

Let’s consider a real-life scenario that explains the idea of regression testing:

When adding a new payment method on an e-commerce website, ensuring a seamless user experience is crucial. Regression testing is re-executing the previous tests to check that the new payment type hasn’t caused any new issues or reintroduced any old ones.

This involves testing the functionality of the new payment feature and examining how it interacts with existing features like the shopping cart, order processing, and customer account management. By re-running these tests, you can ensure that the entire website remains robust, reliable, and free of unintended side effects, giving customers a secure and hassle-free shopping experience.

Why is regression testing important in Agile and CI/CD?

Regression testing is crucial in Agile and CI/CD (Continuous Integration/Continuous Delivery) environments due to the iterative nature of these development methodologies.

Here’s why:

Frequent code changes

In Agile and CI/CD, development cycles are characterized by short and frequent code changes. Regression testing is vital to systematically validate that new features or modifications don’t inadvertently introduce defects or disrupt existing functionalities. The iterative nature of Agile benefits from regression testing as it ensures that each incremental update contributes to the overall stability of the software.

Rapid development iterations

Agile development emphasizes quick and iterative cycles, where regression testing becomes a cornerstone. By conducting frequent regression tests, development teams can swiftly validate changes, preventing the accumulation of bugs that could disrupt the workflow. This iterative testing approach aligns with the Agile principle of delivering functional software at the end of each iteration, ensuring the software remains reliable throughout its evolution.

Continuous Integration

Continuous Integration (CI) involves integrating code changes into a shared repository multiple times a day. Regression testing ensures the integrated code works seamlessly with the existing codebase. By running regression tests continuously as part of the CI process, teams can detect and address integration issues early, maintaining a consistently stable and reliable codebase.

Early detection of defects

In Agile and CI/CD, early defect detection is paramount. Regression testing, integrated into the development pipeline, allows teams to identify and address defects promptly. This early detection reduces the time and effort required for debugging and contributes to a smoother development process by mitigating the risk of critical defects and delaying project timelines.

Ensuring code quality

While Agile and CI/CD prioritize speed, maintaining code quality is equally essential. Regression testing acts as a quality assurance mechanism, ensuring that code changes do not compromise the overall quality and reliability of the software. Providing a potentially shippable product at the end of each iteration supports Agile principles and continually supports the commitment to provide high-quality software.

Automated testing efficiency

Automation is a fundamental aspect of Agile and CI/CD workflows. Automated regression tests, executed rapidly and consistently, provide quick feedback on the impact of code changes. This efficiency accelerates the testing process and allows development teams to focus more on innovation and less on manual testing efforts, contributing to the overall agility of the development cycle.

Types of regression testing

Here are the various types of regression testing:

Corrective regression

Corrective regression testing is conducted in response to fixing a specific defect or issue identified in the software. It involves running tests related to the corrected functionality to ensure the fix does not introduce new problems or negatively impact existing features. This type of regression testing is focused on validating the effectiveness of the corrective measures taken and maintaining the integrity of the software.

Retest-all regression

Retest regression testing involves re-executing all new and existing test cases associated with the modified code. This broad approach ensures that the entire application is thoroughly validated after modifications, providing a comprehensive view of the system’s behavior. While effective, it can be time-consuming, especially in large and complex projects.

Selective regression

Selective regression testing is a targeted approach where only specific test cases related to the modified or impacted areas are re-executed. This type of regression testing optimizes testing efforts by focusing on the most relevant test scenarios, allowing for quicker validation of changes without testing the entire application. It is beneficial when time and resources are limited.

Partial regression

Partial regression testing involves re-running a subset of test cases that cover specific functionalities or modules affected by recent changes. Unlike selective regression, partial regression may include more test cases but focuses on a limited scope. This approach balances comprehensive testing and resource efficiency, making it suitable for projects with moderate time constraints.

Complete regression

Complete regression testing entails re-executing all test cases in the application, regardless of the nature or scope of changes made. This thorough testing approach ensures that any potential side effects or dependencies across different parts of the software are identified. While comprehensive, complete regression testing can be resource-intensive and time-consuming, often requiring careful planning.

Unit regression

Unit regression testing is conducted at the software’s individual component or unit level. It involves retesting specific units of code to ensure that modifications, such as bug fixes or enhancements, do not adversely affect the functionality of those units. Unit regression testing is crucial for maintaining the integrity of isolated code modules and preventing unintended consequences during development.

How to perform regression testing?

Performing regression testing involves systematically validating that recent code changes do not negatively impact existing functionalities.

Here’s a detailed and simplified guide on how to conduct regression testing:

Understand the code changes

Before starting the regression testing, thoroughly understand recent code modifications. Whether it involves adding new features, fixing bugs, or updating existing functionalities, a clear comprehension of these changes is essential. This knowledge is the foundation for selecting appropriate test cases, ensuring a targeted and effective testing process.

Identify test cases

Carefully identify the test cases most relevant to the recent code changes. Focus on scenarios associated with the altered features, resolved issues, or functionalities that the modifications may impact. This strategic selection of test cases optimizes testing efforts, allowing for a thorough yet efficient examination of the software’s integrity.

Create a test suite

Organize the chosen test cases into a dedicated test suite designed explicitly for regression testing. This suite should contain a representative set of scenarios, including positive and negative test cases. Creating a well-structured test suite simplifies the testing process, making it easier to manage and execute the necessary tests during regression testing.

Prioritize test cases

Prioritize test cases based on their significance and potential impact on the application. Begin with high-priority test cases that cover critical functionalities, ensuring that essential aspects of the software are precisely validated first. This prioritization approach facilitates the early detection of critical issues, enhancing the efficiency of the regression testing process.

Execute regression tests

Execute the regression test suite against the updated version of the software. This step involves manually running the selected test cases to validate the recent code changes or through automated testing tools. Automation, particularly in repetitive and time-consuming tasks, ensures quicker and more consistent test execution, enhancing overall efficiency.

Analyze test results

Thoroughly analyze the regression test results to detect discrepancies between expected and actual outcomes. Document and log any defects or issues encountered during testing. This analytical phase is crucial for distinguishing between newly introduced defects and pre-existing problems that may have resurfaced, providing a clear roadmap for the resolution process.

Bug triage and resolution

Collaborate closely with the development team to prioritize and address identified issues. Conduct bug triage sessions to evaluate the severity and urgency of each defect. Once resolved, re-run the affected test cases to validate the effectiveness of the fixes and ensure that the resolution process does not inadvertently introduce new challenges.

Repeat as needed

Regression testing may require regular repetition depending on the development cycle and frequency of code changes. In Agile and CI/CD environments, integrating regression testing into the development pipeline ensures continuous validation of code changes, fostering a proactive approach to maintaining software quality and stability.

Document and report

Thoroughly document the entire regression testing process, including the executed test cases, identified issues, and resolutions applied. Prepare a comprehensive regression testing report summarizing the overall test results. This documentation is a valuable reference and contributes to a well-informed decision-making process regarding the software’s stability and quality.

Challenges and difficulties of regression testing

Cost concerns

Regarding business expenses, allocating a significant amount of time and money toward regular testing is essential. Regression testing, in particular, is a complex process that doesn’t necessarily produce a specific Return on Investment. Managing its importance and commercial benefits can prove to be challenging. However, despite the cost, it’s crucial to prioritize regression testing to secure the necessary budget for testing purposes.

Time pressure

Organizations are increasingly prioritizing the development of high-quality apps and their quick delivery. As a result, regression testing often has time limitations. Testers are typically given a deadline to complete the regression testing process. To keep up with the fast-paced development cycle, testers may have to take risks by prioritizing necessary regression tests and skipping some of the less critical ones.

Incomplete information

Suppose a software testing project is underway, and new software testers are hired to speed up the process or release some of the work. The current testers in the organization may not have enough time to provide detailed information about the app’s functionality and features, existing issues, delivery timing, etc.

As a result, the new testers may need more details on the existing testing effort to begin testing. In such cases, it becomes challenging to establish proper test techniques for practical cooperation. Deciding which tests can be omitted becomes crucial, making it difficult to determine the right approach.

Maintenance challenges

Maintaining and optimizing the current regression test suites can be a challenging task. Whenever there are any modifications, the current regression test suites may require modification by adding, eliminating, or changing the existing test cases. The following tasks need to be finished before the deadline for regression testing. Therefore, optimization and maintenance are two additional challenges that must be addressed.

Comparing regression testing to others

Regression testing vs. retesting vs. User Acceptance Testing (UAT)

Features	Regression Testing	Retesting	UAT (User Acceptance Testing)
Purpose	Ensure recent changes don’t affect existing functionalities	Validate fixed defects from the recent cycle	Verify alignment with user expectations and business requirements
Scope	It may involve automation for efficiency, but manual testing is common	Focused on areas with identified and fixed defects	Comprehensive, simulating real-world usage scenarios
Test Cases	Uses a broad set of test cases, including both new and existing	Concentrated on specific test cases related to resolved defects	Encompasses scenarios aligned with user workflows
Timing	Conducted after every code change for continuous validation	Performed after bug fixes or changes to confirm resolution	Typically, the final testing phase before release
Automation	Often automated for frequent execution and large test suites	Usually, a one-time phase toward the end of development	Primarily manual, considering subjective assessment by end-users
Frequency	Frequent, integrated into Agile and CI/CD development cycles	Occasional, conducted as needed after defect resolution	Usually a one-time phase toward the end of development

Regression testing vs. smoke testing

Smoke testing is a preliminary test conducted to check if the basic functionalities of a newly developed or modified software build are working correctly. It aims to identify significant issues early in the testing process, ensuring that the application is stable enough for further, more in-depth testing.

On the other hand, regression testing is performed to confirm that new changes or additions to the software do not impact the existing functionalities. It involves retesting the entire application or a significant portion to detect any unintended side effects or bugs introduced by the latest modifications.

Commonly asked questions on regression testing

Is regression testing done before UAT?

Yes.

Regression testing is typically conducted before User Acceptance Testing (UAT). It involves retesting the previously tested and stable software parts to ensure they work as expected after introducing new code or modifications. By conducting regression testing before UAT, teams can recognize and resolve issues earlier in the development process, reducing the possibility of major problems occurring during UAT or in the production environment.

The testing process often follows a sequence where developers perform unit testing first, followed by integration, system, and regression testing. After regression testing, UAT is conducted to assure that the software fulfills the business requirements and is ready for release to end-users.

Is regression testing part of UAT?

No.

Regression testing is not typically part of User Acceptance Testing (UAT). Regression testing is conducted earlier in the software development lifecycle to ensure that new code changes do not adversely affect existing functionality. It aims to catch unintended side effects or defects introduced during development.

On the other hand, UAT focuses on validating the software against business requirements and is performed by end-users to ensure that the system meets their needs before release. While regression testing and UAT are essential, they serve different goals at different stages of the testing process.

Is regression testing agile?

Yes.

Regression testing is an integral part of Agile development methodologies. In Agile, frequent iterations and continuous integration often lead to code changes. Regression testing ensures these changes do not introduce defects or negatively impact existing functionality.

It aligns with Agile principles by providing quick feedback on the software’s stability and maintaining the quality of the product throughout the development process. This iterative and incremental approach allows Agile teams to catch and address issues early, facilitating a more responsive and adaptable development cycle.

Is regression testing the same as end-to-end testing?

No.

Regression testing is not the same as end-to-end testing. Regression testing focuses on verifying that recent code changes do not adversely affect existing functionality by retesting specific areas of the software. It aims to catch unintentional side effects or defects introduced during development.

On the other hand, end-to-end testing evaluates the entire application workflow, ensuring that all integrated components work together seamlessly. While both are essential testing methodologies, regression testing is more targeted at specific functionalities impacted by recent changes. In contrast, end-to-end testing examines the overall system functionality from start to finish.

Final thoughts on what is regression testing

In conclusion, regression testing is vital to the software testing process, ensuring that software applications remain robust and reliable throughout their development life cycle. Regression testing is crucial in minimizing risks, enhancing software quality, and supporting agile development practices by systematically verifying existing functionalities after each code change. Its integration into development pipelines and automation tools makes regression testing an essential practice for modern software development teams.

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Regression testing example