Regression Testing in Software Testing

What is regression testing?

Regression testing is a software testing practice that ensures an application still functions as expected after any code changes, updates, or improvements.

Regression testing is responsible for the overall stability and functionality of the existing features. Whenever a new modification is added to the code, regression testing is applied to guarantee that after each update, the system stays sustainable under continuous improvements.

Changes in the code may involve dependencies, defects, or malfunctions. Regression testing targets to mitigate these risks, so that the previously developed and tested code remains operational after new changes.

Generally, an application goes through multiple tests before the changes are integrated into the main development branch. Regression testing is the final step, as it verifies the product behaviors as a whole.

What are the types of Regression Testing?

Regression testing is done through several phases of testing. It is for this reason, that there are several types of regression testing. Some of them are as follows:

Unit Testing

In unit testing when coding changes are made for a single unit, a tester, usually the developer responsible for the code – re-runs all previously-passed unit tests. In continuous development environments, automated unit tests are built into the code, making unit testing very efficient in comparison to other types of testing.

Progressive Testing

This type of testing works effectively when there are changes done in the software/application specifications as well as new test cases are designed.

Selective Testing

In selective testing testers use a subset of the current test cases to cut down the retesting cost and effort. A test unit must be rerun if and only if any of the program entities it covers have been changed.

Retest-All Testing

This type of testing strategy involves the testing of all aspects of a particular application as well as reusing all test cases even where the changes have not been made. It is time-consuming and is not much use when any small modification or change is done to the application.

Complete Testing

This testing is very useful when multiple changes have been done in the existing code. Performing this testing is highly valuable to identify unexpected bugs. Once this testing is completed, the final system can be made available to the user.

It is very important to know which type of testing suits your requirement. Next up, we will discuss how regression testing is implemented.

How is Regression Testing Implemented?

The procedure to implement regression testing is like the one you apply for any other testing process. Every time the software undergoes a change and a new release comes up, the developer carries out these steps as part of the testing process:

  • First of all, he executes unit-level regression tests to validate code that they have modified, along with any new tests they have written to cover new or changed functionality
  • Then the changed code is merged and integrated to create a new build of the application under test(AUT)
  • Next, smoke tests are executed for assurance that the build is good before any additional testing is performed
  • Once the build is declared good, integration tests are performed to verify the interaction between units of the application with each other and with back-end services such as databases
  • Depending on the size and scope of the released code, either a partial or a full regression are scheduled
  • Defects are then reported back to the development team
  • Additional rounds of regression tests are performed if needed

That’s how regression testing is incorporated into a typical software testing process. The image below clearly depicts how regression testing performed.

When do we do Regression Testing?

Interviewers may ask you why do you do regression testing. We do software regression testing whenever the production code is modified. Usually, we do execute regression tests in the following cases:

Some regression tests examples are here.

1. When new functionalities are added to the application.

Example: A website has a login functionality which allows users to do login only with Email. Now the new features look like “providing a new feature to do login using Facebook”.

2. When there is a Change Requirement (In organizations, we call it as CR).

Example: Remember password should be removed from the login page which is available earlier

3. When there is a Defect Fix.

Example: Imagine Login button is not working in a login page and a tester reports a bug stating that the login button is broken. Once the bug is fixed by the developers, testers test it to make sure whether the Login button is working as per the expected result. Simultaneously testers test other functionalities which are related to login button

4. When there is a Performance Issue Fix.

Example: Loading the home page takes 5 seconds. Reducing the load time to 2 seconds

5. When there is an Environment change.

Example: Updating the Database from MySQL to Oracle)

Regression Test Tools

Some of the Regression Test Tools are:

1. Selenium


3. SahiPro

4. TestComplete

5. Watir

6. IBM Rational Functional Tester

Why is regression testing automation required?

Regression testing automation is needed to ensure changes in the application do not disrupt currently functioning parts of the application. Given there are tests (e.g. core features, critical functionality) that need to be repeatedly executed in each regression test run, it is required that these regression test cases are automated.

Why regression testing automation is important in Agile software development methodology?

Agile methodology focuses on building a high-quality product, reducing the risk associated with development. Since agile methodology involves frequent changes, it is important to have a regression test automation process for the same

Few Benefits of Regression Testing

  • Regression testing increases our chances of detecting bugs caused by changes to a software and application- either enhancements or defect fixes. Also keep one thing in mind that we also don’t give any sort of guarantee that for performing regression testing there are never any sort of side effects also.
  • Regression testing also detects undesirable side caused always by changing the operating environment.
  • The set about regression test is much useful for a new way about doing integration testing. This new mode is quite faster and little confusing than the old way about doing integration testing- but you always need some sort of set about regression test to do it.