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Guide to Regression
Testing

Regression testing is a high-stakes activity: if your application falls after you make one change, imagine what would happen if you add ten more! Read on to learn everything you need about regression testing - from its importance to challenges and more.

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What Is Regression Testing?

Regression testing is a vital process that checks if the existing functionalities of software still work as expected after any changes have been made. The process involves retesting the functionalities previously tested to identify any defects or changes that affect the system′s stability or functionality. The purpose of regression testing is to ensure software stability and reliability during development or maintenance.

Example: A software team develops an e-commerce website. The testing team creates 1000 test cases to check every aspect of the application. After adding new features or updates, the QA team does regression testing by creating 100 new test cases and re-executing the previous 1000. This ensures the website works as intended and maintains software quality.

What is Non-Regression Testing?

Non-regression testing is a software testing technique that verifies whether a new or modified functionality works properly without affecting the previous functionality. This technique involves testing only the unit or module that has been modified instead of testing the entire product, which helps to save time and resources.

Difference between Regression Testing and Non-Regression Testing

Regression TestingNon-Regression Testing
The aim is to prevent past bugs.The aim is to identify bugs in new functionality or features.
Focuses on the stability of the existing system.Focuses on validating newly added functionality.
Ensures that past changes do not negatively impact existing functionality.Ensures that new functionality or features are working as intended.
Performed after bug fixes, updates, or changes.Usually performed after the completion of new functionality or features.
Occurs after changes to the software are made.It occurs during the development process or after new features are released.
Requires existing test cases to be re-executed.Requires new test cases to be developed and executed.

Why Regression Testing?

Regression testing is a critical testing practice or method that helps maintain software stability, minimize risks, and ensure that changes made to the codebase do not negatively impact existing functionalities.It is vital in delivering high-quality software that meets user expectations and business requirements.

Types Of Regression Testing

The following are the different types of regression testing that are commonly used in software development.

  • Corrective regression testing is used when no modifications are made to the product′s specification.

  • Retest-all regression testing verifies all system specifications from the origin and reviews every minor change the software has experienced.

  • Selective regression testing identifies how the code behaves when new code is added to the existing code and utilizes a subset of current test cases to lower the effort and cost needed for retesting.

  • Progressive regression testing yields significant outputs when specific modifications are made in the program and new test cases are developed.

  • Complete regression testing is used when numerous updates are performed on the existing code or when the new updates have a distinct impact on the overall software.

  • Partial regression testing validates issues when new code is pushed to an existing one and ensures that a system functions as expected.

  • Unit regression testing is conducted in isolation and mainly focused on code units without any dependencies and interactions.

When Can We Perform Regression Testing?

Regression testing is performed by testers in the following scenarios:

  • When new functionality is added to the software application.

  • When there is a requirement to change.

  • When a defect is fixed.

  • When a functional/performance issue is fixed.

  • When there is a change in the environment.

Top Regression Testing Tools

There are several regression testing tools available in the market, each with its own set of features and capabilities. Here are some of the top regression testing tools widely used in the industry,

  • 1. Testsigma

    Testsigma is a popular regression testing tool used in the software industry. It is known for its AI-powered testing capabilities, which make testing faster, smarter, and more efficient.

    Testsigma

    Here are some of the key features of Testsigma:

    • AI-powered test automation: Testsigma uses AI to create, maintain, and execute tests, making them more effective and efficient.

    • Codeless test creation: Testsigma allows users to create tests without any coding, using a simple drag-and-drop interface.

    • Cross-browser testing: Testsigma supports testing on multiple browsers, making it easy to ensure that your application works seamlessly across different platforms.

    • Parallel test execution: Testsigma allows users to execute multiple tests in parallel, saving time and improving efficiency.

    • Integrations: Testsigma integrates with popular tools such as JIRA, Slack, and GitHub, making it easy to streamline your testing process.

    Overall, Testsigma is a powerful tool that can help you improve your regression testing process and deliver high-quality software faster.

  • 2. Selenium

    Selenium is a widely used open-source framework for automating tests on web browsers and supports regression testing of the same too.

    Katalon
    • You can create test scripts in various programming languages like Java, Javascript, PHP, Perl, Ruby, C#, and Python.

    • It supports browsers like Chrome, Firefox, Safari, Edge, and Internet Explorer.

    • It supports different platforms like Mac, Windows, and Linux.

    • It allows parallel test execution.

    • Selenium can be integrated with test frameworks, such as TestNG, JUnit, or NUnit.

    While Selenium is a powerful tool for regression testing, it is essential to note that it supports only web-based testing. So, you should use other tools like Testsigma for desktop or mobile app testing.

  • 3. Katalon Studio

    Katalon Studio is another popular test automation tool that you can use for regression testing.

    Katalon
    • Katalon supports programming languages, including Groovy and Java.

    • It offers integrations with various applications like Git, Jenkins, and JIRA.

    • It supports various platforms, browsers, and devices.

    • It easily integrates into your CI/CD pipeline.

    • It supports record-and-playback feature to record user actions as test cases.

  • 4. Apache JMeter

    Apache JMeter is another top open-source automated regression testing tool mainly used for performance testing, load testing, stress testing, and functional testing of web applications. JMeter is written entirely in Java programming language. It supports different platforms like Linux, Windows, and Mac.

    Apache-JMeter

How to perform Regression Testing ft. Testsigma

To perform regression testing, software testers first identify and debug any existing bugs before making the necessary changes to fix them. Next, they select relevant test cases that cover both the modified code and the parts of the software that might be affected by the changes. Finally, they execute the selected test cases to verify that the software works as expected, even after code changes. This helps ensure that the fixes do not introduce new issues or regressions.

Regression Test Scenario - Consider that the login functionality of the application with email/password is tested successfully. The software team has now added a new functionality, "Forgot Password".

Now, QAs should test the new functionality along with the old test cases to ensure the overall login functionality works.

That is, if I had written 5 automation test cases to test Sign-in functionality, now I would create 4 more new test cases to test the Forgot Password and then the sign-in. And I would run the new and old test cases to test the entire functionality.

Follow the steps below to test the Forgot Password feature and the application′s overall login functionality in Testsigma.

To perform regression testing, you can start by signing up and creating an account.

Web Application URL - https://id.testsigma.com/ui/login

regression testingregression testing

Note - Below image depicts the previously run test cases for testing the login functionality of the application. Now, we will add or update the test cases to test the overall login functionality of the application along with Forgot password.

Step 1 - Create a new test case using the Create button.

regression testing

Step 2 - Now, start creating test cases using the NLPs. Also, you can easily record the elements from the webpage using the Record Element.

regression testing

Note - Refer to the below gif to know better on how to use Record Element to create test cases.

regression testing

Step 3 - Add the new test cases along with the old test cases. Here, I have created the new test cases for Forgot Password as follows,

regression testing

Step 4 - Click on Run to execute the regression test cases.

regression testing

Step 5 After the test is successful, you can analyze the test results in detail using the logs, screenshots, and video.

regression testing

How Should One Choose Test Cases for Regression

Identifying test cases for regression testing is important because it helps testers focus on critical functionality and avoid re-executing the same tests repeatedly. By prioritizing test cases, we can reduce the cost and time required for test execution, detect faults early on, and ensure the delivery of an exceptional quality product.

According to Priority:

  • Select test cases with frequent defects
  • Choose test cases with critical functionalities
  • Select test cases with frequent code changes
  • Cover end-to-end test flows
  • Cover field validation test cases
  • Select a risk-based testing approach

According to Techniques:

  • Customer requirement based priority: Test cases prioritized based on customer requirements, complexity, and volatility. Higher factor values prioritized.

  • Code coverage based technique: Prioritization based on the portion of code covered during testing. Major part of code tested first.

  • Cost-effective: Test cases prioritized based on cost factor, including regression testing, requirement gathering, test execution, analysis, and prioritization costs. Lower cost cases prioritized.

  • History-based: Prioritization based on test execution history, likelihood of selection determined by previous results.

  • Priority using fault severity: Requirements prioritized based on fault severity, higher weight given to code with potential for more faults.

  • Weight of requirement determined based on various factors, not specified.As per

Tips for Selecting Regression Testing Test Cases

The challenges in regression testing are as follows,

  • Recent code or functional changes.
  • Business requirements mapping.
  • Frequent buggy/defective areas.
  • Visible areas to the user.
  • All integration test cases.
  • All complex test cases.
  • Based on priorities.
  • Based on criticality and impact of bug fixes.
  • Sample of successful and failed test cases.

Regression Testing Techniques

There are several regression testing techniques that can be applied based on the nature of the software and the changes being made. Here are some commonly used regression testing techniques,

Regression Testing Techniques
  • 1. Regression Test Selection

    In this method, we select specific test cases from the test suite for the feature that has to be retested based on the changes made to the code. The test cases are categorized as reusable and obsolete. Reusable test cases can be used again in future regression cycles, while obsolete test cases are no longer used in upcoming regression cycles.

  • 2. Test Case Prioritization

    Instead of re-testing all test cases, this technique focuses on identifying and prioritizing the most critical test cases.

  • 3. Re-test All

    This technique involves re-testing the entire set of existing test cases.

  • 4. Hybrid

    This is a combination of Regression Test Selection and Test Case Prioritization methods. That is, instead of selecting the entire test suite, we only select the test cases that are re-executed based on their priority.

  • 5. Corrective Regression Testing

    It helps ensure the existing code works correctly and checks if the current test cases are usable. When the test results turn positive, QAs can be confident that the test cases are effective and up-to-date. It also allows QA to proceed with test planning and prioritization while incorporating new code changes into the testing process.

  • 6. Progressive Regression Testing

    It is a testing approach where QAs recognize that code changes may require changes to the test suites. So, they will work on updating the test scripts to align with the new requirements. This method is used when a change affects the product vision.

  • 7. Selective Regression Testing

    Selective regression testing is performed to observe how the code behaves when new code is added to the program. Here, a subset of test cases is selected based on the impacted areas of the software that have been modified.

  • 8. Partial Regression Testing

    Partial regression testing helps identify issues that may arise when newly written code is integrated into existing code. It ensures that the application's performance has not been impacted because of new code.

Why is Regression Testing Important in Agile and CI/CD?

CI/CD involves a series of automated tests that enable continuous testing while continuously pushing or integrating new code. This approach allows for frequent releases, resulting in faster feedback loops and avoiding the chance of broken code near the production date.

Even small changes in the software can have a big impact on its key functions. Regression testing helps align with the Agile testing methodology, here and tests for the impact of the new code.

Also, regression testing goes beyond just checking the core product functionality. It can also involve analyzing the software for optimization and improving the user experience (UX). For example, it can identify defects and suggest ways to enhance the UX.

Besides functional testing, visual regression testing helps detect even the slightest UI bugs that may occur due to code changes. For example, it helps identify issues such as non-clickable buttons, alignment issues, font size issues, and more.

Rather than manually reviewing each UI element across various devices and browsers, automated regression testing can quickly locate these visual bugs.

Simply put, regression testing helps maintain the integrity and reliability of the software throughout the development process. It ensures that the existing functionalities remain intact, bugs are caught early, and the software is continuously deployable, supporting the rapid delivery of high-quality software.

Regression Testing and Configuration Management

Configuration management is crucial during regression testing in Agile environments, where code is continuously modified. To ensure your regression tests are effective, follow the below guidelines,

  • The code that is being tested must be managed by a configuration management tool. It helps ensure proper version control and helps maintain a record of changes made.

  • Avoid making any changes to the code during the regression test phase. It helps maintain the integrity of the tests.

  • Isolate the database used for regression testing. It helps ensure consistent and reliable test results.

Advantages Of Regression Testing

Regression testing offers several advantages in software development, including,

  • The primary advantage of regression testing is its ability to detect regressions that may have been introduced into the software due to new code changes.

  • It helps improve the overall quality and stability of the software application.

  • It helps make sure that new code changes or other bug fixes do not impact the existing functionalities.

  • It helps improve customer satisfaction.

  • It ensures that previously fixed issues do not reoccur.

  • By conducting thorough regression testing, the risk of software failure or poor user experience due to regression issues is significantly reduced.

  • Automated regression testing accelerates the testing process and helps achieve faster results than manual testing.

Disadvantages Of Regression Testing

While regression testing offers several advantages, it also has some potential disadvantages, like,

  • Regression testing has to be done even for small code changes, as they might affect the existing functionality.

  • It is time-consuming and resource-intensive, especially when executed manually. Running many test cases, particularly in complex systems, can increase the required effort and time.

  • The regression test suite must be constantly updated and maintained as the software evolves and new features are added.

  • It can be challenging to achieve complete test coverage in regression testing, especially when changes affect a wide range of functionalities or modules.

  • While regression testing helps identify regressions, it does not guarantee the absence of all defects.

  • Over time, as the software evolves and new test cases are added, there may be redundancy in the test suite.

Regression Testing Best Practices To Follow

There has been a lot of debate among testing professionals regarding how many regression checks are necessary. A low amount of regression may lead to bugs being missed in production, while too much of it can burden testing teams. Therefore, it is crucial to strike a balance that provides adequate test coverage through a combination of a thorough approach and several best practices for regression testing. These practices are listed below:

1. Reduce Regression Impacts – Plan Small & Frequent Releases

As Regression issues may occur because of the changes done to the existing application code; hence the more the code changes in a release, the more would be the probability of increased regression impacts.

The development team should be encouraged to release frequent code changes to the testing environment.

2. Understand the AUT/Product better

It is important for the QA team to have a thorough understanding of the application in order to identify areas that may be more susceptible to issues resulting from new changes. One way to achieve this is by preparing story cards for each module and connecting them to show the relationship between them. This will make it easier to determine which module will be affected by changes made to another module.

3. Involve QA in Code Reviews

It is highly recommended to include the Quality Assurance (QA) team in code reviews. While they don′t need to scrutinize the code in detail, it is beneficial for them to have an understanding of the areas that were modified. This knowledge can aid in identifying areas that require continuous updates and facilitate the detection of regression issues in the future.

4. Dev-QA Pairing

Apart from being involved in code review, QA can also collaborate with developers during the development of new modules. This provides an excellent opportunity for the QA teams to take notes and plan their regression suites, ensuring maximum test coverage for the release.

5. Use Defect Tracking Systems to Document

In today′s agile development environment, where there is a focus on more frequent software releases, it is crucial to keep track of any issues that arise during testing. This information can then be used to create regression test plans. One of the best practices for regression testing involves addressing the problem of insufficient documentation. To do this, the issues should be documented in detail with supporting evidence, which can later be used to create automated test cases.

6. Identify the Regression Test Coverage Right

To identify regression test candidates, consider the high-risk areas, core features, and basic workflow of the application under test. It′s also helpful to include test cases that uncovered defects in previous cycles. Rather than exhaustive testing, create a logical set of test cases. Keep the regression test suite updated as the application evolves.

7. Automating Regression Suites

Grooming the regression suite is an ongoing process that starts when the application is launched and continues indefinitely. The suite may consist of thousands of test cases to achieve comprehensive test coverage. However, if done manually, this can create a huge workload for the test teams.

To avoid this, it is recommended to deploy an automation tool framework to run the regression packs and quickly report any code changes that break the application to the development teams. This approach significantly reduces testing efforts and enables the identification and resolution of issues in a timely manner.

Challenges in Regression Testing

The challenges in regression testing are as follows,

  • As regression testing progresses, test suites tend to grow in size. However, due to limitations in time and budget, it becomes difficult to execute the entire test suite.
  • Determining the frequency of regression tests, such as after every modification, build update, or bug fix, poses a challenge and requires careful planning.
  • Finding a balance between minimizing the test suite while ensuring maximum test coverage is a challenge.

Retesting vs Regression Testing

Retesting and regression testing are two distinct testing activities that serve different purposes in the software testing process.

Here is a detailed comparison between re-testing and regression testing,

CriteriaRe-testingRegression Testing
DefinitionThe process of executing test cases that failed in previous test cycles to verify if the issues have been fixed.The process of re-executing selected test cases to ensure that the software still functions correctly after any new changes have been made.
PurposeFocuses on executing test cases related to fixed defects or failures.To ensure that the software still works correctly and that existing functionalities have not been negatively impacted by the changes.
ScopeFocuses on executing test cases related to fixed defects or failures.Focuses on executing test cases related to the new areas of the software.
Test Cases SelectionOnly the failed test cases from the previous test cycle are re-executed.A subset of test cases is selected based on the impacted areas of the software that have been added/modified.
Test TypeUses the same environment as the previous test cycle.Uses an environment that closely resembles the production environment, including hardware, software, and network configurations.
Test DataIt may require specific test data related to the previously failed test cases.It may require a range of test data to cover different scenarios and ensure adequate coverage of the impacted functionalities.
Test Execution OrderThe failed test cases are given priority and executed first.The test cases related to the changed or impacted areas are given priority, followed by other relevant test cases.
TypeIt is a planned testingIt is a generic testing
TimeframeTypically performed immediately after the fixes have been implemented.Performed after changes have been made to the software, usually during the regression testing phase.
AutomationYou can not automate test cases for retestingYou can automate regression tests, and it saves time and effort.
Test CoverageFocuses on the specific areas where defects or failures were reported.Focuses on a wider range of test cases to cover the impacted functionalities.
Time Taken It is not much time consuming as it tests only the test cases related to bug fixingIt is quite time-consuming as it tests the overall functionality of the software
Bug detectionIt makes sure that the original fault is corrected. It checks for unexpected side effects.