regression testing

“Quality is never an accident; it is always the result of intelligent effort”. -John Ruskin

Businesses often introduce new features and updates to their software and applications as part of their strategy to enhance employee and customer satisfaction levels. 

A prime example is ING, the multinational financial services company, which regularly releases features to its web and mobile sites every three weeks, resulting in remarkable improvements in its customer satisfaction ratings.

For agile businesses, continuous upgrades and innovations are crucial. However, it is equally important to ensure that the end-user experiences a seamless application experience. 

In this blog, we will explore regression testing in-depth, including its definition, importance, and the various tools and methods used in its execution. 

So let’s dive into the world of regression testing and uncover the tools, examples, and methods that make it a crucial aspect of software development.

What is Regression Testing of Software?

Regression testing is an essential software testing practice that aims to ensure that an application continues to function as intended after any updates, code changes, or improvements.

The primary goal of regression testing is to maintain the overall stability and functionality of existing features. Whenever there is a modification in the code, regression testing is employed to ensure that the system remains sustainable under continuous improvement.

Code changes can introduce dependencies, defects, or malfunctions that may impact the application’s performance. Regression testing aims to mitigate these risks, ensuring that the previously tested and developed code remains operational even after new changes.

Typically, an application undergoes multiple tests before changes are integrated into the primary development branch. Regression testing is the final step in the process, as it verifies the product’s behavior as a whole.

Regression testing is generally employed in the following situations:

  1. When a new requirement is added to an existing feature.
  2. When a new feature or functionality is introduced.
  3. When defects are addressed by fixing the codebase.
  4. When the source code is optimized to improve performance.
  5. When patch fixes are incorporated.
  6. When there are configuration changes.

Why is Regression Testing Important?

In software development practices, test automation is a crucial element. Similarly, automated regression testing is also considered an essential component.

By implementing a rapid regression testing process, product teams can receive more insightful feedback and respond promptly. Regression testing can detect new bugs early in the deployment cycle, eliminating the need for businesses to incur costs and maintenance efforts to fix accumulated defects. 

Sometimes, even a seemingly minor modification can have a cascading effect on the product’s core functions.

Therefore, developers and testers must ensure that no change, no matter how small, is left outside the scope of their control.

Functional tests only evaluate the behavior of new features and capabilities, neglecting their compatibility with existing ones. Therefore, without regression testing, it becomes more challenging and time-consuming to investigate the root cause and architecture of the product.


When your product experiences frequent changes, regression testing serves as a means to maintain quality by verifying the product’s functionality as it is enhanced.

Types of Regression Testing

Types of Regression Testing

1. Unit Regression Testing

refers to a testing method where the code is tested as a single entity, and if there are any minor changes made, testing is done only on the affected module and its dependent components. Testers do not need to search for the areas of impact, and existing test cases can be modified or rewritten.

2. Regional Regression Testing

involves testing the areas of the software that are affected by new feature releases or major enhancements to existing features. This testing method includes testing the changing unit and the impact area. 

Test cases are rewritten, old test cases are deleted, and new ones are added to the test case repository. 

Dependent features may also be affected, so it is necessary to identify the impact areas and test the dependent modules using old test cases.

3. Full Regression Testing

is a comprehensive testing method that involves testing both the changed unit and independent old features of the application. 

This testing method is mostly used for life-critical or machine-critical applications, and it is also done during the product/application development stage.

4. Release Level Regression Testing

refers to testing during the second release of an application. It is done when organizations want to add new features or enhance existing ones, and a new release needs to be launched. 

This type of regression testing is focused on the impact area, and regression test cases are identified accordingly.

5. Build Level Regression Testing

refers to testing during the second build of an upcoming release. It is done whenever there are changes to the code or bug fixes across builds. QA retests the bug fixes first, then the impact area. 

This process continues until a final stable build is obtained and given to the customer or when the product is launched. QA uses their product knowledge to identify the impact areas.

How To Do Regression Testing?

How to do Regression Testing

1. Identify the scope of changes: Understand the updates or modifications made to the software application, including bug fixes, new features, or performance improvements.

2. Determine the impact: Assess the potential impact of these changes on existing functionality and identify the areas of the application that may be affected.

3. Update the test suite: Review and update the existing test suite to include new test cases or modify existing ones as necessary to cover the changes.

4. Select test cases: Choose the appropriate test cases for regression testing, which may involve using one or more of these techniques such as:

    • Retest All:

This approach to Regression Testing involves running all the tests within an existing test suite or collection. It can be quite costly, as it demands substantial time and resources.

    • Selective Regression Testing:

This is a method where only specific test cases from the test suite are executed to verify if the updated code has any impact on the software application. Test cases are divided into reusable ones, which can be employed in future regression cycles, and obsolete ones, which cannot be utilized in subsequent cycles.

    • Test Case Prioritization:

Test cases should be prioritized based on their business impact and the importance and frequency of the associated functionalities. By selecting test cases according to their priority, the overall size of the regression test suite can be significantly reduced.

    • Hybrid:

The hybrid approach combines Selective Regression Testing and Test Case Prioritization. Instead of choosing the whole test suite, only specific test cases are selected for re-execution based on their priority levels.

5. Execute the test cases: Run the selected test cases using manual or automated testing tools, depending on the complexity and frequency of regression tests.

6. Analyze the results: Evaluate the test results to identify any issues or unexpected behaviors caused by the changes. If any defects are found, report them to the development team for resolution.

7. Repeat as necessary: Regression testing is an ongoing process, so it should be conducted regularly throughout the software development lifecycle. As new changes are made, the regression test suite should be updated, and tests should be executed to ensure the application’s quality and stability.

8. For example, Let’s clarify with an example. Consider the following scenario:

Release 1 Statistics:

  • Application Name: XYZ
  • Version/Release Number: 1
  • Requirements: 10
  • Test Cases: 100
  • Development Time: 5 days
  • Testing Time: 5 days
  • Testers: 3

Release 2 Statistics:

  • Application Name: XYZ
  • Version/Release Number: 2
  • Requirements: 15 (10 existing + 5 new)
  • Test Cases: 150 (100 existing + 50 new)
  • Development Time: 2.5 days (half the workload compared to the previous release)
  • Testing Time: 7.5 days (5 days for existing test cases + 2.5 days for new requirements)
  • Testers: 3

Release 3 Statistics:

  • Application Name: XYZ
  • Version/Release Number: 3
  • Requirements: 20 (15 existing + 5 new)
  • Test Cases: 200 (150 existing + 50 new)
  • Development Time: 2.5 days (half the workload compared to the first release)
  • Testing Time: 10 days (7.5 days for existing test cases + 2.5 days for new requirements)
  • Testers: 3

Observations from this scenario include:

  • Functionality increases with each release.
  • Development time doesn’t necessarily increase with releases, but testing time does.
  • Companies and management are often unwilling to invest more time in testing than development.
  • Increasing the number of testers isn’t always the solution, as it incurs additional costs and training time, and may compromise quality.
  • Reducing regression testing could be risky for the software product.

Due to these factors, Regression Testing is a strong candidate for Automation Testing, but it doesn’t have to be exclusively performed in that manner.

Regression Testing in Agile

Agile is a flexible methodology that employs iterative and incremental processes. The product is developed in short cycles called sprints, which usually last 2-4 weeks.

With numerous iterations in Agile, regression testing is crucial, as changes to functionality or code are made during these iterations.

The regression test suite should be created from the beginning and updated with each sprint.

Regression testing in Agile can be categorized into two types:

#1) Sprint Level Regression

It focuses on the new functionality or enhancements implemented in the most recent sprint. Test cases are chosen from the test suite based on the added functionality or improvements made.

#2) End-to-End Regression

It comprises all the test cases that must be re-executed to evaluate the entire product by covering all its core functionalities.

Since Agile involves short sprints, it’s essential to automate the test suite. Test cases must be executed repeatedly within a limited time frame. Automation helps reduce execution time and minimizes the risk of defects slipping through.

Regression Testing Vs Re-Testing 

For those new to automation, the terms re-testing and regression testing may seem confusing and alike. However, these two concepts are entirely distinct from one another.

Aspect Re-testing Regression Testing
Purpose To verify if the identified defects have been fixed in a previously failed test. Ensure that new changes or bug fixes do not negatively impact existing functionality.
Test Cases Executes only failed test cases from the previous testing cycle. Executes a set of test cases to validate existing functionality after changes.
Focus Target specific defects and their fixes. Focuses on the entire software application and potential side effects from changes.
Trigger Performed after a defect has been fixed or a failed test case has been resolved. Conducted after any changes or updates to the software application.
Frequency Conducted as needed when defects are fixed. Typically conducted as part of regular software development and maintenance cycles.
Scope Narrow, focused on the specific issue that has been fixed. Broader, covers all impacted areas of the software due to changes.

The following are some of the most popular regression testing tools:

1. Selenium: A widely-used open-source tool for automating web browsers. It supports multiple programming languages, including Java, C#, and Python.


2. JUnit: A widely-used testing framework for Java applications, JUnit is designed to help developers write and execute unit tests and regression tests.


3. TestNG: A testing framework inspired by JUnit and NUnit, TestNG is designed specifically for Java applications, with additional features and support for parallel test execution.

4. NUnit: An open-source unit testing framework for .NET applications, NUnit is used for writing and executing regression tests in C# and other .NET languages.


5. Pytest: A popular Python testing framework, Pytest is used for writing and executing various types of tests, including unit, functional, and regression tests.

RSpec: A popular testing framework for Ruby applications, RSpec is used for behaviour-driven development (BDD) and supports writing and executing regression tests.

6. HP Unified Functional Testing (UFT): A commercial testing tool by Micro Focus (formerly HP), UFT supports both GUI and API testing and is used for functional and regression testing of applications.

HP Unified Functional Testing (UFT)

7. Katalon Studio: A versatile testing tool that supports web, mobile, and API testing, Katalon Studio can be used for both manual and automated regression testing.

Katalon Studio

8. TestComplete: A commercial testing tool by SmartBear, TestComplete supports multiple scripting languages and allows for the creation and execution of regression tests for desktop, web, and mobile applications.


9. Ranorex Studio: A commercial testing tool for desktop, web, and mobile applications, Ranorex Studio provides an all-in-one solution for creating and executing regression tests.

Ranorex Studio

10. IBM Rational Functional Tester (RFT): A commercial testing tool by IBM that supports various technologies, including Java, .NET, and web-based applications, and offers script-assisted automation and data-driven testing capabilities.

Rational Functional Tester (RFT)

11. Apache JMeter: Apache JMeter is an open-source tool primarily for load and performance testing of web apps, services, and APIs. While not designed for regression testing, it can be combined with other tools to execute regression test suites when performance is vital.

Apache JMeter

Challenges of Manual Regression Testing

A primary challenge of Regression Testing is determining the areas impacted by changes in the software. Other challenges include:

  • Time-consuming due to the growth in test cases with each release.
  • Requires additional manual QA Engineers.
  • Repetitive and tedious tasks, leading to potential accuracy concerns.

Test Automation is introduced to address these challenges.

Benefits of Test Automation:

  • Time-efficient: Executes test cases in batches, enabling parallel processing of multiple cases.
  • Reusable: Allows test scripts to be reused in subsequent releases with similar impact areas.
  • Cost-effective: Eliminates the need for extra resources to repeatedly execute similar test cases.
  • Accurate: Machine-based processes are less likely to make errors due to oversight.

Limitations of Test Automation:

  • Test automation cannot be applied to new features, as test scripts must still be written by Test Automation Engineers.
  • Automation is not applicable when a feature is updated.
  • Technology support, like Captcha, may not be available.
  • Human intervention is necessary for some cases, such as OTP.
  • In certain situations, test automation may take longer than manual testing. For example, if 5 test cases take 1 hour to execute manually, test automation requires 5 hours for the same cases.


Regression testing plays a vital role in enhancing the product’s overall quality and user experience. Utilizing appropriate regression testing tools can effectively detect and resolve defects early in the development process.

Moreover, incorporating regression testing in Agile provides numerous technical and business benefits. The more your organization invests in planning and executing regression testing, the greater control you will have over the product’s budget, process, and error prevention.

Ready to ensure the quality of your software products? Contact Scrum Digital today to learn how our expert team can help you streamline your regression testing process and deliver superior software products with confidence. 

Don’t wait, get in touch now and take your testing to the next level!

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