Regression testing: A complete guide to software stability

An extensive guide to regression testing

Software updates, especially in complex solutions, are tricky and should be handled with care to ensure they don't break the entire system. Imagine releasing a minor update, a new feature, or a bug fix only to realize this minor change has created issues with key features and functionalities of the software. This is where regression testing plays an important role—it helps maintain the stability of the software by testing every functionality after an update. It's a crucial part of the software testing lifecycle, especially in CI/CD and agile environments where constant updates occur.

What is regression testing?

Regression testing is a type of software testing that verifies whether code changes made to the system, such as bug fixes, new features, or updates, don't impact the existing functionality.

How is regression testing used in software development?

When you introduce new changes or features into any software or application, they can affect the existing functionality. These minor changes can result in crashes, glitches, and loss of software functionality, either partially or fully.

Regression testing helps in detecting these errors after every new code change and ensures there's no effect on the stability of the application. It's an on-going process that's done after every code change. The impact of these new features or changes are assessed by both functional and non-functional testing.

Regression testing mainly focuses on two aspects of the code alterations:

• Whether the new change behaves as intended.
• Whether the new changes unintentionally affect other components.

For example, in an ecommerce app, if developers update the product search page, every other critical functionality, such as cart management, checkout, and payment gateway pages, are checked for defects or errors. This involves rerunning previous test cases on existing functionality to confirm everything works as expected.

Regression testing can be done manually, but automated testing tools like Zoho QEngine make regression testing more efficient, scalable, and affordable in terms of both time and money.

Why is regression testing important?

Regression testing helps to make sure that the system in its new state is working properly. Regression testing also helps mitigate the risks of collateral damage occurring from any new changes made to the system. Here are some reasons to run regression testing:

• Enhance stability: Regression testing prevents unexpected bugs or issues from sneaking into the software while also enhancing software stability.
• Increase reliability: It delivers improved quality by testing current and past functionality.
• Supports CI/CD: It's integral to the continuous integration/continuous deployment pipeline and agile environments, where updates occur frequently.
• Improves customer satisfaction: Regression tests prevent the release of updates with errors, ensuring a seamless user experience.

When is regression testing done?

When there are updates to software or apps, regression testing is done to understand if it's breaking any other component or affecting overall functionality. Some common scenarios for running regression testing include:

• After adding new enhancements, features, versions, or updates to existing functionality.
• After fixing bugs or correcting errors After software optimization or performance enhancements.
• After changes in environments, such as configurations or dependencies.
• During routine software maintenance to check for hidden bugs and catch defects early.

Examples of regression testing

Here are some practical examples of how regression testing works:

• A banking app upgrades its account transactions: Let's say a banking app updates its feature that enables the user to schedule future transactions, and this update involves the entire transaction processing logic. Here are some regression tests that should be performed:
  • Test depositing, withdrawal, and fund transfer features.
  • Verify that scheduled transactions are processed properly.
  • Ensure that transaction history, statements, and all other details are displayed properly.
• A social media app enables a video-sharing feature: This will be about testing if existing features, such as image sharing and text posts, work without any issues—videos play across various browsers and operating systems, and comments, likes, and the share section work correctly. API testing will also be conducted to ensure media processing doesn't initiate unnecessary latency.
• A healthcare management app updates its login system with two-factor authentication: In this scenario, the tester checks if all other login functionalities work properly, password recovery functions well, the feature works on various devices, and that linked accounts are accessible after the change.

Regression testing techniques

Regression testing protects existing functionality by tracking down errors or bugs after the code changes and alerting the development teams. These techniques primarily have the same goal—identifying flaws and bugs—but with differing approaches:

• Retest all: Retesting all of the code using previous test cases and running all test scenarios to identify regressions.
• Regression test selection: Running test cases only on components that might be affected by the code changes.
• Test prioritization: Collecting all test cases and prioritizing them based on their importance and risk.
• Hybrid regression testing: Combining regression test selection and regression test prioritization; also the most successful technique for regression testing.

Regression testing types

Here are some of the types of regression testing that can be used based on what the tester is looking for:

• Unit regression testing tests how individual units perform and is best for smaller tests, as they give a detailed view of how the code performs. It also helps detect bugs and flaws early on in the software development process.
• Partial regression testing runs only a subset of the regression test suite, mainly based on code changes.
• Selective regression testing analyzes the impact of new code on already existing functionality. This technique checks for the effects of both new and existing code. This is chosen only when a few select components must be checked rather than the entire system.
• Progressive regression testing is a continuous process of regression testing that happens throughout the project lifecycle. This helps identify any regressions early, reducing the cost of fixing them at a later stage.
• Corrective regression testing is usually done when there are no new modifications to the source code. It tests the overall app functionality using the test cases that are available.
• Complete regression testing checks how multiple changes made to the code are affecting the root code. This is most often done before launch and can highlight if any of the new changes are impacting how the root code performs.
• Retest all regression tests is the most comprehensive of all regression techniques. It involves re-executing all previously run test scenarios on the new code.
• Regional regression testing tests certain areas affected by the new change or modification and analyzes the improvements in a particular area to see if any reliable components are broken.

How to perform regression testing

Whenever software undergoes a change—a new version, update, or release—there's a need to check its impact on existing modules. Here’s how regression testing works:

1. Identify the code changes or modifications: This helps understand the scope of regression testing through impact analysis. Emphasize critical functionalities and high-risk areas.
2. Prioritize test cases: Try to prioritize test cases that are affected by the changes. If necessary, update the test cases depending on the changes made.
3. Choose a testing approach: Choose between manual testing and automation testing. Test automation is ideal for regression testing, as it is easily scalable, reduces human error, and can be performed on large data sets with ease. Automated testing is also ideal for continuous integration/continuous deployment loops where constant changes are made.
4. Set up the test environment: Prepare the necessary data required and ensure the test environment reflects the production setup.
5. Execute the tests: Run the chosen test cases, then compare the results to the expected outcomes and record defects or errors.
6. Analyze the results: Examine the results of the test, review and rework them to fix the errors, then run them again.
7. Continuous regression testing: Integrate regression testing into CI/CD pipelines for continuous validation of code changes and schedule regression test runs using scalable automated tools like Zoho QEngine.

How to prioritize test cases for regression testing

It's important to prioritize critical business functions, high-risk areas, and frequently used features:

• Critical functionalities, such as checkout, cart, and payment and order pages.
• Frequently used sections, such as the search bar.
• Areas that have frequent defects.
• High-risk areas and customer-reported issues.
• Recent bug fixes and modified areas

Why is regression testing crucial in agile and CI/CD environments?

Changes happen at a rapid pace in agile and CI/CD environments, where there are expectations of constant deployment of new and high-quality features or updates. Regression testing helps understand the defects and gets them fixed quickly through faster feedback loops. Regression testing helps maintain software stability and reduces the risk of defects while helping seamlessly roll out new features in agile and CI/CD environments.

Automated regression testing vs. manual regression testing

Automated testing uses tools and test scripts that help run repetitive tests easily with minimal effort or error. Manual testing uses human testers who are often manually executing each test case. Though both manual and automated regression testing can be used depending on the test scenarios, here’s a detailed comparison of both:

The need for an automated regression testing tool

Automated regression tools help save time and money while ensuring delivery of a bug-free, high-quality product. With test automation, regression tests can be done in various environments, perform repetitive tests easily, and identify defects early in the software development lifecycle. This enables quicker bug fixes and faster time-to-market. Automated regression testing is a boon to CI/CD pipelines, as it helps with early detection of bugs, faster feedback loops, and constant validation of code changes.

How can Zoho QEngine help with regression testing?

Zoho Qengine is a powerful test automation tool that simplifies the creation, execution, automation, and analysis of regression test suites. It's ideal for organizations working in both agile and CI/CD environments. Some of the key features include:

• Quick test case creation and support for low-code automation.
• Impeccable test execution through cross-platform testing, multiple execution environments such as local or on the cloud, and self-healing AI to detect flaky tests, which improves test stability.
• Comprehensive test analysis to quickly identify bugs, analyze trends, and track defects.
• Automated regression suite management, advanced test planning, and scheduling

Benefits of regression testing

Regression testing helps organizations deploy high-quality software. Here are some of its benefits:

• Helps find bugs at an early stage in the development cycle.
• Increases the chance of detecting bugs.
• Validates code changes and helps in researching unwanted side effects due to modifications.
• Improves software stability and reliability by continuously testing to identify and rectify defects.
• Reduces risk associated with new feature deployments or upgrades.
• Facilitates a better user experience and increases confidence in the software.
• Leads to more efficient use of resources

Regression testing is time-consuming and expensive when performed manually, but an automation testing tool helps optimize regression testing for any organization.

Best practices for regression testing

• Prioritize test cases with a focus on critical functionality, business impact, and user interactions.
• Automate repetitive tests to save time and reduce manual error.
• Integrate with CI/CD pipelines to detect issues early on.
• Focus on maintaining and storing test data for future analysis.
• Refine and update test cases depending on the changes made.
• Foster collaboration between teams to minimize delays and ensure the regression testing is effective

Final thoughts on regression testing

Regression testing plays a vital role in maintaining software stability, reliability, and performance and is an essential part of the software development lifecycle. It ensures every new bug fix, update, or feature doesn't create unintended damage to existing functionality.

By integrating automation tools like Zoho QEngine, organizations can reduce the risk of bugs or defects slipping into production and improve their efficiency and user experience. With the increasing complexity of modern software applications, automated regression testing is a necessity to ensure a high quality user experience.