What is Regression Testing? (Definition, Test Cases, Examples)

What is Regression Testing and How Does it Work?

Regression testing is a sort of testing that is used to ensure that a software update does not affect the product's current functioning.

This is to guarantee that any new functionality, bug patches, or modifications to current features don't break the product. In order to validate the effect of the modification, previously performed test cases are re-executed.

Regression Testing is a sort of Software Testing in which test cases are re-run to see whether the application's prior functionality is still functioning and if the new changes have caused any new defects.

When there is a major change in the original functionality, even if it is only a single bug repair, a regression test may be run on a new release.

Regression refers to retesting the elements of the program that haven't changed.

When Should Regression Test Be Performed?

Regression testing is frequently done after modifications or new features have been verified. This isn't always the case, however. Regression tests must be included in the daily test cycle for the release that will take months to complete. When Functional Testing for the modifications is completed for weekly releases, regression tests may be run.

A variant of retest is regression checking (which is simply to repeat a test). The cause for retesting might be anything. Assume you were testing a certain feature at the end of the day, and you were unable to complete the test and were forced to halt the process without determining whether the test succeeded or failed.

When you return the following day, you repeat the exam - this indicates you are repeating a test you have already completed. A Retest is the simple process of redoing a test.

A regression test is essentially a retest. Something in the application/code has changed especially for this unique occasion. It might be code, design, or anything else that determines the system's general structure.

The Regression Test is a kind of retest that is used in this circumstance to ensure that the modification hasn't impacted anything that was previously functioning.

The most typical reason for this is because new versions of the code were developed (due to an expansion in scope/requirement) or problems were resolved.

What is the purpose of the Regression Test?

When a programmer patches a defect or adds new code for a new feature to the system, regression occurs.

The newly introduced and existing functionality may have a lot of dependencies.

This is a quality check to see whether the new code is compatible with the old code so that the unmodified code isn't harmed. The testing team is usually tasked with checking the system for any last-minute alterations.

Testing just impacted the application area in such a case is required to finish the testing process on time while covering all important system elements.

When there is a continual change/improvement in the application, this test is critical. The additional feature should not have a detrimental impact on the code that has already been tested.

Regression is necessary to locate issues that have arisen as a result of a code modification. If this testing is not done, the product may have major flaws in the real world, putting the client in danger.

The tester reports a problem with the Price of the Product not appearing properly, i.e., it displays a lower price than the real price of the Product, and it has to be addressed as soon as possible.

Once the developer has fixed the problem, it must be re-tested, and regression testing is also required, because while the price on the reported page may have been corrected, it may still be showing an incorrect price on the summary page, where the total is displayed alongside the other charges, or in the email sent to the customer.

If this testing is not done, the consumer will suffer a loss since the site calculates the total cost with the wrong pricing and sends the same amount to the customer through email. The consumer will lose money if the product is offered online at a cheaper price after the customer approves.

As a result, testing plays a significant role and is both necessary and useful.

Regression Testing Types

The numerous forms of regression are listed below −

  • Unit Regression − During the Unit Testing phase, code is tested in isolation, which means that any dependencies on the unit to be tested are disabled, allowing the unit to be tested independently without any discrepancies.

  • Partial Regression − Partial regression is used to ensure that the code continues to function properly even after modifications have been made to it and the unit is merged with other code that is unmodified or already exists.

  • Complete Regression − When a change in the code affects a number of modules and the effect of a change in another module is unknown, complete regression is used. The whole product is regressed to see whether there are any modifications as a result of the altered code.

Techniques for Regression Testing

The numerous approaches are listed below.

Retest Everything

As the name implies, the full test suite is re-run to guarantee that no issues have arisen as a result of a change in the code. This approach is more costly than the others since it involves more time and money.

Choosing a Regression Test

Test cases from the test suite are chosen to be re-executed in this technique. It's not like the whole suite has been re-run. The test cases are chosen based on the changes in the module's code.

There are two types of test cases: reusable test cases and obsolete test cases. Reusable test cases may be reused in subsequent regression cycles, but outdated test cases will not be utilized in subsequent regression cycles.

Prioritization of Test Cases

High-priority test cases are conducted first, followed by medium- and low-priority test cases. The importance of a test case is determined by its criticality and influence on the product, as well as the functionality of the product that is utilized most often.


Regression Test Selection and Test Case Prioritization are combined in the hybrid approach. Select just the test cases that are re-executed based on their priority, rather than the whole test suite.

Selection of Regression Tests

Regression Test Selection is a method in which a subset of test cases from a test suite is run to see whether the updated code has any impact on the software application. Test cases are divided into two categories − reusable test cases that may be reused in subsequent regression cycles and outdated test cases that cannot be reused.

Test Case Prioritization

Prioritize the test cases based on their business effect, criticality, and frequency of usage. The regression test suite will be considerably reduced if test cases are prioritized.

Regression testing test cases selection

According to industry statistics, a large proportion of defects reported by customers were caused by last-minute bug patches that had unintended consequences, making picking the Test Case for regression testing an art and not a simple task. The following test scenarios may be used to create effective regression tests −

  • Test scenarios with a high number of flaws

  • Users will be able to see more features if they are more visible.

  • Test scenarios that test the product's fundamental characteristics

  • Case studies of functionalities that have experienced significant and recent alterations

  • All Test Cases for Integration

  • All Extensive Test Cases

  • Cases of boundary value tests

  • A number of successful test examples are shown below.

  • A selection of failure test scenarios

The different benefits of the regression test are listed below.

  • It enhances the product's quality.

  • This guarantees that any bug patches or additions made do not affect the Product's current functioning.

  • This testing may be done with the help of automation technologies.

  • This will guarantee that problems that have previously been resolved do not recur.

Example of Regression Testing

We'll use a project involving the development of image processing software to demonstrate how regression tests are carried out.

The discussion will be based on a real-world situation and will cover both manual and automated regression testing.

But first, let's look at some real-world instances of how this test differs and what it focuses on;

  • Bug Regression − This is where bugs that have been claimed to be resolved are retested.

  • Old fix method − Issues and problems that have previously been addressed are all retested to ensure that those areas are still functional. Regression was created with this goal in mind.

  • Conversion/Port method − The software is moved to a different platform in this case. The next step is to run a regression test to see whether the transferred software was successfully integrated. The majority of the changes will be made to the newer environment rather than the previous one.

  • Configuration method − In this case, a newer version of the application or device is introduced, and the program is executed on or in conjunction with it. Conversion testing is quite similar to this case. Still, only the environment and a few components associated with the program in issue change, not the original code or platform.

There are several automation tools available for automating regression test cases; nevertheless, the tool should be chosen based on the project's needs. Because the Regression test suite must be updated often, a tool should be able to update the test suite.

With that, we'll conclude our discussion and expect that there will be much more clarity on the matter moving forward.

Updated on: 20-Dec-2021

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