How to Perform Regression Testing?

In this article, we will learn what is regression testing, how to do it, when it is required and its types.

What is Regression Testing?

Regression testing is also known as black box testing. It is used to verify that a software code modification does not affect the product's existing functionality. Regression testing ensures that a product's new functionality, issue patches, or other changes to an existing feature work properly

Regression testing is a sort of software analysis. Test cases are re-run to ensure that the application's previous functionality is still operational and that the new changes haven't introduced any defects.

When there is a significant change in the original functionality, regression testing can be performed on a new build. It ensures that the code continues to function even though modifications are made. Regression testing refers to re-testing the elements of the application that haven't changed.

The Verification Method is another name for regression tests. Many test cases are automated. Test cases must be run multiple times, and manually repeating the same test case over and over is time-consuming and monotonous.

How to do Regression Testing?

When software maintenance includes upgrades, error fixes, optimization, and deletion of existing functionalities, regression testing is required. These changes may have an impact on the system's functionality. In this instance, regression testing is required.

The following strategies can be used to perform regression testing −

Re-examine All

One method for performing regression testing is to use Re-Test. All test case suits should be re-executed in this method. We can define re-testing as when a test fails and the cause of the failure is determined to be a software flaw. After the problem has been reported, we can anticipate a new version of the software with the flaw rectified. In this instance, we'll need to run the test again to ensure that the problem has been resolved. This is referred to as re-testing. This is referred to as confirmation testing by some.

The re-test is quite costly, as it necessitates a significant amount of time and resources.

Regression analysis Selection

  • Instead of executing a full test-case suit, this technique executes a single test-case suit.

  • The chosen test case is split into two parts: (a) Test cases that can be reused and (b) Test cases that are no longer valid.

  • Test cases that are reusable can be used in subsequent regression cycles.

  • Test cases that are no longer valid cannot be used in subsequent regression cycles.

Test case prioritization

Prioritize the test case based on the business effect, important functionality, and frequency of use. The regression test suite will be reduced by selecting test cases.

Cases When Regression testing should be done

In the following case, regression testing can be performed −

When a Change Requirement exists

Example − Remember password has been deleted from the login page, which was previously relevant.

When the application receives new functionality.

Example − A website offers a login feature that only allows users to log in using their email addresses. We've added a new option that allows you to log in using Facebook.

When the flaw has been corrected

Example − Consider the following scenario: a login button on a login page isn't working, and a tester reports a bug indicating that the login button is broken. Once the bug has been repaired by the developers, the tester verifies that the Login Button is functioning as expected. On the other hand, Testers also test the other functions correlated to login button.

If there is a performance problem to fix

Example − A homepage takes 5 seconds to visit; by reducing the load time to 2 seconds, the page will load in half the time.

When an environment change is there

Example − When the database is upgraded from MySQL to Oracle.

How do you decide which test cases to use for regression testing?

It was discovered during an inspection of the industry. The customer reported multiple faults that were caused by last-minute bug patches. As a result of these side effects, picking a Test Case for regression testing is an art, not a simple operation.

Regression test can be done by −

  • A test case which has frequent defects

  • Functionalities which are more visible to users.

  • Test cases checks the main features of the product.

  • All integration test cases

  • All complex test cases

  • Boundary value test cases

  • A sample of successful test cases

  • Failure of test cases

Regression Testing Types

The following are the various types of regression testing −

  • URT stands for Unit Regression Testing.

  • RRT stands for Regional Regression Testing.

  • FRT stands for "Full or Complete Regression Testing."

Unit Regression Testing (URT)

We'll only test the altered unit in this case, not the impact area, because it could influence other modules' components.


The developer creates the Search button in an application, which allows 1-15 characters in the first build. The test engineer then uses the test case design technique to test the Search button.

The customer now requires that the Search button support 1-35 characters, as well as some other changes to the need. The test engineer will just test the Search button to ensure that it accepts 1-35 characters and will not examine any other aspects of the first build.

Regional Regression Testing (RRT)

This is known as Regional Regression Evaluating, and it involves testing the modification together with the effect area or areas. We're testing the impact area because if there are dependable modules, they'll have an impact on the other modules as well.

Consider the following scenario:

We can assume that there are four separate modules in the image in our mind which includes Module A, Module B, Module C, and Module D, which are provided by the developers for testing during the first build. Now it's up to the test engineer to find the faults in Module D. The developers get the bug report, and the development team remedies the defects then after sends the second build.

The preceding flaws are fixed in the second build. The test engineer now realizes that the problem fixes in Module D have had an influence on some functionality in Modules A and C. As a result, the test engineer checks the impact areas in Module A and Module C after testing Module D, where the bug has been resolved. As a result, this type of testing is referred to as Regional regression testing.

Full Regression Testing (FRT)

During the product's second and third releases, the client requests the addition of three to four new features, as well as the correction of some bugs from the previous release. The testing team will next do an impact analysis and determine that the above change will require us to test the complete product.

As a result, we may refer to testing the updated features as well as all of the remaining (old) features as Full Regression testing.

When the following conditions are met, we will perform the FRT −

  • When the alteration is made to the product's source file. JVM, for example, is the JAVA application's root file, and any changes to JVM will cause the entire JAVA program to be tested.

  • When we have a large number of modifications to make.