In 2016, Nest Thermostat encountered a significant setback when an upgrade caused its software to malfunction across all devices. This unfortunate incident occurred during one of the coldest weekends, leaving customers without heat. The root cause of this problem was the need for proper Regression Testing before the software upgrade was implemented.

Testing is often viewed as a secondary aspect of software development. However, it is just as important, if not more important, than the development process itself. This is because a flawed application with various features can result in financial losses and decrease the user base.

To ensure that software is of the highest quality, WTA Studios offers Software Testing and QA Services. Our team helps companies deliver and release the best product in the market. Our service includes various types of testing, such as regression testing, conducted before a product’s final release. This testing evaluates whether the app functions as expected after any feature changes or significant upgrades.

This blog will provide an in-depth look at regression testing, including its test cases, types, tools, and all other necessary information. Let’s dive in!

What Is Regression Testing?

Regression Testing is a type of testing where the software’s existing functionality is verified to ensure that changes made to the codebase do not negatively impact it. These changes include adding new features, fixing bugs, or updating current features. In other words, regression testing involves re-executing previously passed test cases against the latest software version to ensure that all functionalities are still working correctly. It is important to note that regression testing is a series of tests and not just a single test performed whenever new code is added.

Regression Testing Example

To better understand the importance of Regression Testing, let’s use a hypothetical example. Imagine that you are a software development firm and have been assigned a project to create an image and video editing application. After completing the initial build with the core features, you conduct regression testing with 1000 test cases to ensure that the app works correctly. Once the app passes the regression tests, you send it to the client for feedback.

However, you also need to run the 1000 old test cases to ensure that the core features are not affected.

This is a typical scenario for regression testing. While it may seem time-consuming to verify every small code change against the product’s core features, it is necessary to ensure that the software remains functional and of high quality.

When Is Regression Testing Performed?

Regression Testing is typically performed when:

  • A new feature has been added
  • An existing element is modified
  • A bug is fixed
  • The software is upgraded

The software’s environment changes (e.g. operating system update). It is important to conduct regression testing in these scenarios to ensure that the software’s existing functionality is not negatively impacted.

Pros And Cons Of Regression Testing


  • Regression Testing ensures that changes to the codebase do not negatively impact other software functionalities.
  • It helps to prevent previously fixed issues from reoccurring.
  • It serves as a risk mitigation strategy during the testing process.
  • The concept of regression testing is easy to learn, understand, and analyze.


  • With automation, regression testing can be quick.
  • It must be performed for every small change made to the codebase.
  • The repetitive nature of the process may affect the agile sprint schedule.
  • Complex test cases must be created for regression testing.

While Regression Testing helps to deliver robust products and mitigate risks, it is also a cumbersome process. Therefore, weighing the pros and cons before deciding to implement it is essential. Additionally, it is crucial to be aware of the challenges that come with regression testing to be able to address them effectively.

Challenges In Regression Testing

challenges in regression testing

High Upfront Cost: Regression Testing can be very time-consuming if done manually. Automation is preferred, but it requires high-end infrastructure and tools, which can be costly.

Testing Approach: Choosing the right testing approach is crucial for the success of regression testing. Having skilled resources and tools is important, but it cannot be accessible without a proper plan for when and how to conduct regression testing.

Enormous Scope and Coverage: The success of Regression Testing depends on the type of test cases suite that is built. The regression suite needs to be updated between every build and release, and remembering every change can be hard for testers, making it challenging to cover all elements.

Complexity: As the number of builds and releases increases, the number of test cases also increases, making the regression test suite more complex. Testers need to test new cases as well as old cases all the time.

While we have covered the basics of regression testing, the question remains of how to implement this testing approach in practice despite these challenges. The next section will explore this aspect in more detail.

How To Conduct Regression Testing?

There is no set pattern for conducting Regression Testing, but there are popular methods that a QA analyst should keep in mind.

Step 1: Regression Test Selection The first step is to select the test cases that need to be retested. Not all test cases in the suite will be tested, and the selection will depend on the module where there is a change in the source code. The test cases are divided into (i) Reusable Test Cases and (ii) Obsolete Test Cases. Reusable test cases will be used for future regression cycles, while obsolete test cases will not be considered for future testing cycles.

Here are some tips for identifying reusable test cases:

  • They are highly error-prone.
  • They verify the functionality of the app.
  • They contain features that are visible to users.
  • They have a recent change in the source code.
  • They have been successfully conducted in the past.
  • They have failed in earlier testing stages.
  • They are related to integration.
  • They are related to boundary values.

Step 2: Determine the Time for Executing Test Cases The next step is to estimate the time it will take to execute the selected test cases. Factors that affect the execution time include:

  • Test data creation.
  • Regression test planning by the QA team.
  • Review of all test cases.

Step 3: Identify the Test Cases that can be Automated. Based on the experimental testing results, the QA team can decide which test cases can be automated. Automated test cases are faster than manual testing and can be re-used repeatedly. Divide the test cases into two groups: (i) manual and (ii) automated test cases.

Step 4: Test Cases Prioritization All test cases are gathered and prioritized as high, medium, and low. The priority depends on the product’s functionality and user involvement. The priorities are divided into:

Priority 0: The most critical test cases, including all core functionalities.

Priority 1: Essential features but outside of core functionality.

Priority 2: Test cases related to technical debt.

Step 5: Executing Test Cases Finally, it is time to execute all test cases to ensure that the product works as it should. Manual or automated testing can be chosen based on the requirement. For automated regression testing, functional testing tools such as Selenium, QTP, Watir, etc., can be used to execute test cases faster.

Now that you have an idea of how to execute regression testing, the next question to consider is the popular regression testing methods. This will be covered in the next section.

Regression Testing Methods

There are four primary Regression Testing methods:

Regression Test Selection: The test cases that need to be retested are selected.

Test Case Prioritization: All test cases are gathered and prioritized.

Retest All: The entire regression test suite is retested.

Hybrid: A combination of the Regression Test Selection and Test Case Prioritization methods.

Out of these methods, the hybrid method is the most effective as it combines the benefits of both test selection and prioritization. This allows for more efficient use of time and resources.

While understanding these methods is important, creating an effective regression testing suite is also essential. The following section will cover this in more detail.

How To Create An Effective Regression Testing Suite?

A Regression Testing suite is a set of test cases designed to ensure that your software functions correctly after any changes or updates. Here are five steps to creating an effective regression testing suite.

Step 1: Prioritizing Regression Tests To create an effective regression testing suite, it is essential to prioritize test cases. Test cases for core features should be prioritised, such as those related to the back-end engine, API, database, etc. The second priority should be given to the rest of the application, and the third to test cases related to technical debt.

Step 2: Developing Smoke Test High-priority test cases should be assigned a smoke test label and executed daily every two weeks or with every build. These test cases can also be automated if desired.

Step 3: Utilizing Manual Testing Certain functions that a user interacts with daily do not require automated workflows for every test. In these cases, manual test cases are sufficient.

Step 4: Testing Integrations A regression test suite with integrations such as APIs, backend engine functions, database connections, data feeds, etc., should be executed. This ensures that all business logic is working well by validating the integrated processes that the application requires.

Step 5: Taking Performance into Account The application’s performance should improve or remain consistent with each release. Therefore, it is essential to conduct a performance test of the product or app before releasing it to the market.

The next question to consider is which type of regression testing should be applied to this testing suite. This will be covered in the next section.

Types Of Regression Testing

Corrective regression testing: It is used when there is no change in the application’s source code. The aim is to verify that the current system works correctly by testing existing functionalities and their related test cases rather than writing new ones.

Advanced testing: It is used when new components are introduced into the system. This testing type helps verify that changes do not adversely affect the old parts by modifying testing requirements and building unique test cases.

Selective: In selective testing, the test coverage is limited to a selected group of test cases already created. Instead of retesting the whole system, only a few chosen components are tested.

Partial testing: It is used to gauge the effect of adding new components to the system. This type of testing examines the impact of changes by testing new functionalities alongside old ones.

Complete testing: It means testing the entire system at once. It is similar to acceptance testing and checks whether the user experience is compromised due to adding one or multiple modules. Complete testing is done just before the final release of the product.

Retest-All testing: It involves re-executing all test cases in the testing suite to ensure that there are no bugs due to changes in the source code of an application. This testing requires more time and effort from the QA team compared to other types.

Now that you understand the various regression testing services the QA team can perform, it’s also essential to know the tools available for regression testing. The following section will cover this topic in more detail.

Top Regression Testing Tools

Selenium: A widely used browser-based or cross-platform regression testing software that provides automated test scripts through datasets and is suitable for large-scale quality assurance testing.

Katalan Studio: An end-to-end regression automation testing solution that simplifies the testing process for experienced and novice testers.

Watir: An open-source regression testing tool written in Ruby, known for its easy-to-read and understandable test cases and interactive capabilities for website testing.

IBM Rational Functional Tester: A testing automation tool by IBM that supports various testing methods such as regression, functional testing, and data-driven testing.

Apache JMeter: An open-source regression test automation software that measures test case performance and provides a regression testing suite for end users.

AdventNet QEngine: A widely used regression automation testing tool for web applications that provides multi-platform support.

Subject7: A cloud-based, enterprise-level regression automation testing tool for desktop, web, and mobile applications that supports high-scale parallel execution.

TimeShiftX: An innovative regression automation testing tool that helps companies gain a competitive advantage by shortening test cycles and reducing resource requirements.

Cerberus Testing: A 100% open-source regression testing automation tool for web and mobile APIs that requires minimal coding.

Testsigma: An automated testing tool that is ideal for regression testing, allows for scriptless test cases written in plain English, and supports CI/CD workflows.

Regression Testing Vs Retesting

Regression testing and retesting are two different testing methods often used interchangeably, but they have other purposes and goals.

Regression Testing Regression testing is a method where the QA team verifies that the changes made to the software do not negatively impact the existing functionality. This type of testing is done to ensure that the new changes stay within the current functionality of the software.

Retesting, on the other hand, is a method of testing where the QA team re-executes previously failed test cases to confirm that the issues have been fixed. This testing ensures that previously identified bugs have been resolved and the software is working as expected.

The main difference between regression testing and retesting is that regression testing ensures that new changes do not break the existing functionality while retesting is done to confirm that previously identified bugs have been fixed. Both methods are important for ensuring the quality of the software, but they serve different purposes and goals.

Regression Testing And Agile Methodology

Regression testing is crucial in agile methodology, as it ensures that new features or updates to the source code do not negatively impact the existing functionality of the product. In elegant, regression testing can be conducted at sprint and end-to-end levels. Sprint-level regression tests the impact of new functionality added in the latest sprint. End-to-end regression re-executes all completed test cases to ensure all core functionalities are working as expected. Due to the short sprints in agile, regression testing must be performed frequently, and automation can be used to reduce execution time and identify frequent defects. It is essential to prepare the regression test suite from the initial stages of the product development cycle and to continue to use it until final deployment.