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Why do you need regression testing & how to successfully perform it?

Why do you need regression testing & how to successfully perform it?

Let’s imagine a real-life situation: you drive the car to the car wash, drive out in a clean car, but after find a scratched trunk near the house. The consequences, financial & moral, could have been avoided by making a general inspection of the car at the car wash. The same situation could happen during software development. In the process of developing a new feature or adding updates to the code, you can see that the application displays unexpected outcomes. In such cases, regression testing is indispensable. We figure out in more detail what it is.

What is regression testing and why is it crucial

Regression testing is one of the major types of software testing. It is used to verify the correctness of additions and ensure that the changes made did not cause errors in the part of the app that wasn’t changed. Regression testing determines that the software continues to meet the established requirements and successfully interacts with other systems after any new improvements, changes, and bug fixes. It basically consists of re-running already performed test cases to make sure that the app performs as expected.

Regression checks play a key role in full-cycle testing and help reach the following goals:

7 ways to perform regression testing

Generally, distinguish the following types of regression testing:


The most expensive type because rerunning the entire test suite from the scratch requires more time, resources, and effort.

Corrective regression. 

One of the simplest forms of regression testing with minimal effort. Only existing functionality and related test cases should be tested.

​​Unit regression.

The focus is on a single unit code, that is tested in isolation.

Selective regression. 

The definite test cases are chosen for testing.

Progressive regression. 

It is used when new test cases are developed against updated and modified product specifications to meet changing requirements and test cases.

Complete regression. 

It is used when huge changes are made to the current code.

Partial regression. 

Individual modules are tested against existing test cases before being merged into an overall code integration.

Regression testing is recommended to be performed every time after updating the software or application, which may include fixing bugs, merging code, migrating to another OS or database, adding new features, and other changes. If the number of users of the system has increased significantly during the operation of the software, it is recommended to perform regression load testing.

As the complexity of the system increases and the number of functions grows, so do the number of tests and the time to repeat them. Regression testing does not always mean a complete check of all functionality. To guarantee the high quality of released software while maintaining optimal timing and cost, a thoughtful approach is needed to determine the strategy and sufficient regression coverage. First of all, that part of the functionality is checked, where the probability of an error occurring after the changes made is the greatest.

Top challenges of regression testing

Although regression testing has many advantages, there are also challenges in conducting this type of testing.

Growing volume of regression

The amount of regression testing may increase with each new sprint, especially on large-scale projects. To manage it efficiently, it is crucial to review test cases and remove outdated ones. It is worth doing this whenever possible and depending on the frequency of interference in releases. Moreover, this is the first call that it is necessary to perform test automation.

Insufficient communication between project participants

QA engineers, developers, business analysts, and project managers need to interact with each other constantly. Thus, they can better realize the scope of work and ensure that the process is efficient, from designing test documentation to realizing which features no longer require regression.

Test case maintenance

With an increase in the number of test cases, their support becomes more complicated. To lower their maintenance, it is essential to communicate more with business analysts who are aware of the relationships in the business logic of the product and can define inconsistencies in test cases if changes are made.

Preliminary cost and time

As new features are introduced, the regression test suite needs to be continuously optimized. As the outcome, the number of test cases varies and existing tests need to be re-executed along with new tests that take a long time to run. Parallel testing can be favorable because it allows you to run test cases simultaneously against different browsers and OS, saving you lots of time. Via Zebrunner Selenium Grid thousands of tests will be run in parallel for less than an hour.

Things to keep in mind when implementing regression testing

  1. Prepare a test plan. This phase includes the selection of the necessary test cases, their further enhancement and refinement, the estimation of the time for creating and running regression tests, the verification of defects, and the design of the final report. It is also crucial to define test cases that could be automated in the future.
  2. Build a regression board. All tasks that QA engineers are working on are placed on the board in order from top to bottom in priority, depending on potential risks, the importance for the client, and a range of other factors. By moving the elements on the board, the team will be always aware of the relevance of tasks and will be able to plan their time efficiently.
  3. Evaluate defect reports. Thus the QA team can get detailed information about the regression tests: the reasons for their failure, the test case steps where the error occurred, logs, screenshots, and interactive videos. Advanced test automation management tools with in-depth reporting capabilities help quickly detect issues and fix them.
  4. Add exploratory testing. Using this type of testing QA engineers can take a new look at the project, extend the test coverage, and find bugs that could have a heavy impact on the end user of the product.
  5. Establish communication on the project. The continuous interaction between QA engineers and product owners helps keep track of changes in requirements promptly. While the communication between QA engineers and developers helps receive feedback about the changes made during the iteration.
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