Articles | August 20, 2023

What is Regression Testing: Unveiling Best Practices and Essential Insights

What exactly is regression testing? Read the article and learn the importance of regression testing in software development and how it ensures existing features aren’t affected by changes.

What is Regression Testing: Unveiling Best Practices and Essential Insights

As the saying goes: „Perfect is the enemy of the good”. But there is also another saying that ”the only constant is change”. In software development, it is impossible to avoid introducing new functions and changes. Often, updating the software is necessary for it to work properly. Verification of changes is an important part of this process – and it’s not only about testing the existing functionalities. Regression testing allows you to ensure that the change has not impacted another, seemingly unrelated part of the software. 

Software development and regression testing 

Let’s imagine that we have an application up and running and available to users. The customer is satisfied because it is popular, and wants to add a new functionality to increase user satisfaction and attract new users. The project team can’t wait to start working: new functionalities, new tasks, new challenges! After deciding on the details, the developers eagerly set to work. Then the testers check the new functionality. After minor improvements, everything works fine. It’s time to make the new functionality available to users. When the day came to release the new version of the application, everyone was happy – the project was completed on time and with the requirements fulfilled. 

Unfortunately, this blissful state of affairs did not last long. A day later, the website was flooded with reports that not all the existing application functions worked properly. The team was surprised: „We didn’t even touch those functionalities, and the new one works fine”. So what went wrong? 

The miserable consequences of not conducting regression tests… 

Well, there was one very important element missing in the testing process. No one checked whether the newly added functionality affected the existing ones. In other words, no regression tests were performed. 

Because of this lack of regression tests, the application didn’t gain new users. Furthermore, the majority of the existing ones stopped using it. It tumbled down the rankings, incomes decreased, which made the client unhappy.  

What exactly is regression testing?

According to the ISTQB dictionary, regression testing is the testing of a previously tested program following modification “to ensure that defects have not been introduced or uncovered in unchanged areas of the software, as a result of the changes made. It is performed when the software or its environment is changed”. 

We can illustrate it this way: during regression tests, we check that „when laying wallpaper in one room, the roughcast did not fall off the wall in the other one”. Any changes to the code in one place can cause the function to break in another, although at first glance it seems that they are not related. That is why it is so important to retest the software after implementing changes.

Red also: Functional testing in software development

How often should regression tests be performed? 

Now you can see how important it is to make sure that the changes have not affected the existing functions and to find errors early on. Changes may result from modifications to the requirements and code of the software, adding new functionalities or repairing a defect, so it is important that regression tests are carried out as often as a new version of the software is released. 

At what levels do we perform regression testing? 

Regression tests are independent of the test levels and test types. They can be carried out at the level of modular, integration, system or acceptance tests and regardless of whether we are dealing with functional or non-functional tests.

nearshore 2023.11.xx graphic 1 1

Creating test cases 

When checking the software, the tester creates test cases. However, not all of them will be performed during regression tests. What does this depend on? 

It mostly depends on the quantity and time needed to run them. If we are dealing with an uncomplicated system and it will not take too much time to perform all test cases while testing regression, then they can be performed. 

Most often, however, systems or applications are characterized by a high level of complexity and are dependent on other systems. We are then unable to use all the created test cases. So what should be the decisive factor when choosing cases for regression tests? 

Selection of regression test cases  

If we have to limit ourselves, it is worth choosing a set of test cases accordingly. Certainly, it’s a good idea to include those cases that: 

  1. Check the most critical functions of an app – first of all, test cases that verify the operation of main functions or functionalities that are often used. 
  2. Were created on the basis of defects – test cases that were created on the basis of reported defects are important. 
  3. Verify the vulnerability to errors – it is worth considering which area of the application is most vulnerable to errors after introducing changes, and also perform test cases from a given area while running regression tests. 
  4. Check the new functionality – don’t forget about test cases that check the newly added functionality. 
  5. Require many steps – let’s bear in mind complex test cases requiring a longer sequence of activities. 

Right Priority 

It is also important to prioritize test cases accordingly. This helps in the selection process, especially when the scope of the test area is large and we don’t have much time to perform them.  

In such a situation, the tester – with time in mind – selects the test cases with the highest priority. This gives us confidence that the most critical areas of the application will be tested. The remaining cases (with a lower priority, which were not performed during regression) should be included in the final report and marked as non-executed. 

How to prioritize test cases? 

There are several factors to consider when prioritizing test cases: 

  • The importance of a given functionality from a business point of view 
  • Its availability / visibility to the end user 
  • The complexity of a given functionality 
  • The financial impact  
  • Whether it was created under time pressure 
  • Whether there were problems with similar functionalities 

Taking into account the above aspects and answering the questions, prioritizing test cases should not be a problem. We will benefit from the work put into this process when the time for testing is very limited. 

Read also: The test pyramid – what, when and how to test software to get profits

Reusable test cases in regression 

The list of test cases selected for regression tests should be verified regularly. Some of them can be used in subsequent regression tests – these are the so-called reusable cases. Others may turn out to be outdated, and thus useless in subsequent regression cycles; such an „outdated case” should be removed from the list of regression tests.  

Verification of whether they are still useful mainly consists in trying to execute a given test case. If the steps described cannot be reproduced or the functionality no longer exists, then such a test case should be removed. It often turns out that the execution path or the expected result has been slightly modified and all you need to do is update the test case. Verification of the set of test cases selected for regression tests is necessary, because leaving outdated test cases gives us a misleading picture of the state of the application in the final reports, and the entire regression process is of no value. 

What do we do when testing regression?  

We check the expected result 

When performing regression tests, we check whether the system behaves as expected. If the regression tests are prepared in the form of test cases, then after completing the steps described in the case, we check whether we get the expected results. 

Verification using a checklist  

Another way to test regression is to prepare a checklist, which is a set of operations in the application that will be tested, saved in the form of short keywords. The checklist is relatively easy to prepare and maintain and is ideal when testers know the application very well and do not need detailed steps. They know what operations should be checked in a given area and what the expected result is. 

Unfortunately, in the case of a checklist, there is a risk that not all operations that should be checked will be tested. To avoid this, it is a good idea to update the checklist while the team discusses the changes to be made. Also, during the testing process of a given functionality, the missing elements should be filled in on an ongoing basis, so that the list is complete during regression. 

What makes a perfect checklist? 

A well-prepared checklist should be concise, and at the same time it should cover all the relevant functionalities. If the system is extensive and the checklist is long, it should be divided into appropriate categories that clearly define the area to be tested. It is also worth making sure that the tested operations are set in the right order, which will speed up the tests and mean that you will not have to go back to check things that have already been checked. Don’t forget that each checklist must be expanded along with the software development. 

Regression vs. retesting – what’s the difference? 

Many people, especially those new to IT, wonder if retests and regression tests are the same thing. 

  • A retest is a single test that checks whether a defect has been removed. It means re-testing of a case in which the final result was different from the expected one and it was reported as a bug and fixed by the programmer. If the system works as expected after correction, we can close the request. However, if we still do not obtain the expected results, the request should still remain open, as it requires further analysis and repair. 
  • Regression is a set of tests, that gives us the answer to whether the entire module or system is free of errors after making changes to the code. Regression tests are much more time-consuming than retests, but let’s also remember that their goal is different. 

How Do You Perform Regression Testing? Automation in regression 

How regression tests are performed depends mainly on how big the system is, and often on what budget we have as well. 

In small projects, when regression tests do not contain a large number of test cases, it is often sufficient to perform tests manually. But what if we have thousands of them and manual work would take months? Or if, during regression tests, there was an error blocking further work and you would have to check everything again after removing it? Then the best solution is to use automatic tests. Regression tests are perfect for automation, mostly because we perform them regularly and automatic tests definitely shorten the time required for executing test cases. If there are thousands of them, automation allows you to save time and effort. 

Read also: Test automation – common myths

Don’t forget about regression testing tools

Of course, the introduction of automatic tests involves costs related to, for example, the purchase of licenses for tools and hiring a person with the right competences. However, these costs in the case of large projects are still much lower than those incurred each time when performing manual regression. 

What if we can’t use test automation? 

Very often, a mixed approach is used in projects, because not every test case allows for automation. Often, complex test cases are troublesome and hard to automate, which is why they are most often performed manually. Of course, it is best if there are fewer cases to be performed manually, and the others are automated – then the regression process runs smoothly and does not take up so much time. 

The Advantages of Regression Testing

The regression testing process requires work and proper groundwork. Undoubtedly, it also implies costs related to time, workload or tools. However, if wisely planned and properly carried out, it brings benefits above and beyond the investment made. Regression testing prevents the introduction of defects to production, which may result in thousands of Euro in losses to the customer. If such a situation occurs, the team must deal with repairing defects, which means that further software development must wait, and is most often postponed. 

The regression test report gives us an answer to the question of whether a given software is of the expected quality and whether it can be implemented in the production. Also, it often indicates modules or areas of the software that are particularly vulnerable to defects, which gives the team the opportunity to thoroughly investigate the problem.   


Regression tests are a very important stage in the software development process, regardless of the methodology of the project, whether it be a cascade or agile approach. They answer the question of what condition our application is in after introducing changes, and allow us to avoid the costs of repairing defects in production. As we already know, the costs of correcting such errors significantly exceed those incurred during the regression testing process. 


What is the purpose of a test case for regression testing?

A test case for regression testing is used for checking the system thoroughly to make sure that changes haven’t caused unintended effects and to guarantee existing functionality is not affected. It is a part of the test suite in the regression testing process, which plays a critical role in the development phase of a software lifecycle.

How can you automate a regression test?

Automating a regression test can be done by using an automated testing tool. This helps in executing the regression test cases repeatedly with minimum human interaction. The main goal of automation in regression testing is to reduce the regression cycle while increasing the efficiency of testing.

What is the difference between retest and regression test?

Retesting is performed to confirm that the defects which were found and reported in the earlier test cycle were fixed. Regression testing, on the other hand, is done to ascertain that the fixes haven’t introduced any new bugs in the previously tested software. Simple put, retesting ensures the original faults have been corrected, while regression testing ensures no new faults have been introduced.

What is a test suite within the context of regression testing?

A test suite in the context of regression testing is a collection of regression test cases that are intended to test a software program to ensure that it functions correctly. The test suite represents the complete regression testing that needs to be performed. It plays a crucial role in validating the overall behavior and functionality of the solution, ensuring no previously resolved bug has been reintroduced.

Can we fully automate regression testing, including the functional test? 

Yes, both regression testing and functional testing, as part of the overall software testing strategy, can be fully automated using automation test tools. Automation enormously accelerates the testing process and raises its effectiveness, especially when the number of test cases is large. However, not everything may be suitable for automation. You should have a balanced mix of manual testing and test automation.

What’s the role of unit testing in the regression testing process?

Unit testing is performed during the development stage to ensure that individual components of the application are working correctly. In the context of regression testing, unit tests make sure that changes made in the software do not affect these individual components, making them an integral part of the regression testing process.

Why is regression testing needed after functional testing in the software testing?

Regression testing is required after functional testing to ensure that the recent program changes have not adversely affected existing features. Functional testing ensures that the requirements are met by the application, whilst regression testing ensures that these functionalities continue to work after changes in code, design or configuration are done.

Can the regression testing be done without automation?

Yes, regression testing can be done manually. However, as the application grows and the number of regression test cases increases, it can become time-consuming and error-prone. Hence, automating regression testing can assist in executing repetitive tasks quickly and efficiently, reducing the regression cycle and increasing testing coverage.

What is a regression testing strategy?

A regression testing strategy involves identifying the need for regression testing, defining the regression test suite (which includes deciding on the number of test cases), and choosing between manual regression testing and automating the regression tests. The test strategy may vary depending on the software’s complexity, changes in functionalities, available resources, and time constraints.

What is the importance of retesting and regression testing in the testing process?

Retesting and regression testing both play major roles in the software testing process. Retesting is done to verify the defect fix, while regression testing is performed to check for unexpected side-effects. Combined, retesting and regression testing ensure the robustness and reliability of the software under test.

A bug tracker for almost a decade, she is also familiar with business analysis and customer contact. Privately, she is a fan of crime stories in all forms: from paper versions, through films, to interactive crime stories in the form of escape rooms.

Exclusive Content Awaits!

Dive deep into our special resources and insights. Subscribe to our newsletter now and stay ahead of the curve.

Information on the processing of personal data

Exclusive Content Awaits!

Dive deep into our special resources and insights. Subscribe to our newsletter now and stay ahead of the curve.

Information on the processing of personal data

Subscribe to our newsletter to unlock this file

Dive deep into our special resources and insights. Subscribe now and stay ahead of the curve – Exclusive Content Awaits

Information on the processing of personal data

Almost There!

We’ve sent a verification email to your address. Please click on the confirmation link inside to enjoy our latest updates.


If there is no message in your inbox within 5 minutes then also check your *spam* folder.

Already Part of the Crew!

Looks like you’re already subscribed to our newsletter. Stay tuned for the latest updates!

Oops, Something Went Wrong!

We encountered an unexpected error while processing your request. Please try again later or contact our support team for assistance.

    Get notified about new articles

    Be a part of something more than just newsletter

    I hereby agree that Inetum Polska Sp. z o.o. shall process my personal data (hereinafter ‘personal data’), such as: my full name, e-mail address, telephone number and Skype ID/name for commercial purposes.
    I hereby agree that Inetum Polska Sp. z o.o. shall process my personal data (hereinafter ‘personal data’), such as: my full name, e-mail address and telephone number for marketing purposes.

    Read more

    Just one click away!

    We've sent you an email containing a confirmation link. Please open your inbox and finalize your subscription there to receive your e-book copy.

    Note: If you don't see that email in your inbox shortly, check your spam folder.