A Detailed Guide to Regression Testing

Serena Gray
4 min readApr 11, 2022


What is Regression Testing?

Regression Testing is one type of testing used to determine if a modification to the program does not affect the current features of the product. This ensures that the software is functioning properly with new features, fixes to bugs or any modifications to the current feature. Test cases that have been previously executed are recreated to determine the impact of the changes.

When should you conduct this test?

Regression Testing is generally conducted following the verification of any changes or additions to functionality. However, this may not be the situation. If the release is taking months to finish, regression tests have to be included in the daily test cycle. Regression tests for weekly release could be run after Functional Testing is over for the modifications.

Regression testing can be described as a variant of Retest (which is simply a way to run a test again). When you are retesting it could be for any reason. For instance, you were trying out one particular feature, and it was nearing the final day of your test and you were unable to complete the test and you had to put the test down without deciding whether the test was passed or failed.

The following day, when you return for the next day, you take the test again, which means that you’re repeating the test you took before. Repetition is a simple process of repeating a test known as a Retest.

A regression test, at its heart, is a kind of retest. It’s only used for the occasion when something in the code or application has changed. It could be code, design, or any other thing that influences the general design of the system.

A Retest is performed in this case to ensure that the alteration did not have an effect on something that was functioning before is known as "the Regression Test.

The primary reason this is done is that updated versions were developed (increase in scope/requirements) or if bugs are resolved.

Why is there a Regression Test?

Regression happens by a programmer fixes an issue or introduces a brand new program to add a new feature to the program.

There could be a variety of dependencies between the newly added functionality and the functionality already in place.

This is a method to determine if the new code is compatible with the previous code so that the original code isn’t affected. Most of the time, the testing team is responsible to verify the most recent modifications to the system.

In this scenario testing, just the application’s area is essential in order to complete the testing within the timeframe required by testing all the main components of the system.

This test is crucial when there is continuous modification or improvement made to the software. The new function will not adversely affect the code that is already tested.

Regression is essential to discover the issues that have occurred as a result of a change in code. If the testing isn’t performed, the software could encounter issues that are critical in the real-world environment, and this could make the customer a target for trouble.

When testing any website The tester will report an issue where the price of the Product isn’t being displayed properly i.e. it displays an inferior price to the actual cost of the product, and the issue must be addressed in the near future.

After the developer has fixed this issue, the system will need to be tested again. Regression Testing is required, in order to verify the cost on the report page is correct but could still show an error on the page, where the total amount is listed together with other costs or the letter addressed to the customer shows the wrong price.

In this scenario, the buyer will be required to pay for the loss in the event that this test is not completed as the website determines the total cost by using the wrong price. The same price is sent to a customer via email. If the customer agrees to the product, it is then sold online for sale at a reduced price, and it’s an expense for the buyer.

Thus, testing plays a major role and is vitally required and essential.

Regression Testing Types

Below are the different types of regression :

  • Unit Regression
  • Partial Regression
  • Complete Regression

1) Unit Regression

Unit Regression occurs in the unit testing stage and the tests are conducted in isolation i.e. all dependencies on the unit that is being tested are removed so that the unit is tested on its own without discrepancies.

2) Partial Regression

Partial Regression is used to ensure that the code is working as expected even if the changes have been made to the code and are integrated into the original or previously existing code.

3) Complete Regression

Complete Regression occurs when a change in code is implemented in a variety of modules, and also when the impact of the modification in another module is not clear. The whole product is examined to determine any changes due to the code change



Serena Gray

I work as a Senior Testing Specialist at TestingXperts. I am a testing professional accustomed to working in a complex, project-based environment.