Regression Test vs Unit Test: Key Differences

May 17, 2024Kiruthika Devaraj
Regression Test vs. Unit Test Key Differences

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Regression testing is a software testing process that involves verifying the functionalities of an application or system after modifications have been made that could impact its performance. Unit testing is a software testing process that involves thoroughly testing individual functions or modules of a program using specialized tools. Unit testing helps testers to catch bugs early in the development process when they can be addressed more efficiently. This blog is about Regression Test vs Unit Test.

We know testing has become a necessary part of the software development life cycle. With the rise of Agile and DevOps methodologies, developers must deliver software faster than ever without sacrificing quality. We must do testing more efficiently and with higher precision. Regression testing and unit testing are 2 types of testing that we talk about, in this blog. We’ll talk about their benefits, main differences, and other important stuff to help you tell them apart easily.

Regression Test vs Unit Test

What is Regression Testing vs. What is Unit Testing?

These two types of testing have different objectives. Also, they require different skills, tools, and techniques.

What is Unit Testing?

Unit testing isn’t anything new. It’s been around since the early days of programming, you know. Testers use unit testing to test individual pieces of code or “units” and ensure they function as expected. This approach helps catch errors or bugs early in development, making fixing them easier and less costly.One example of unit testing is testing a function that calculates the sum of two numbers. The test would involve providing two numbers as input and verifying that the output is the correct sum of those numbers. For example, if the input numbers are 4 and 6, the output should be 10. This testing approach helps ensure that each unit works as intended and can be integrated into a larger system without issues.

What is Regression Testing?

Regression testing is a software testing process that involves verifying the functionalities of an application or system after modifications have been made that could potentially impact its performance. We do this to ensure that the modifications or updates have not broken any existing functionality and to confirm that there are no unexpected side effects.

You can conduct regression testing manually or through automation tools. Regression testing plays an essential role in the software development life cycle since developers continuously make new modifications to an application’s codebase.

For example, a web application has significantly updated its user interface. The testing team would need to verify that all previously functional features, like the home page, login page, cart, checkout, payment etc, still perform as expected and that the new user interface does not introduce any defects. By conducting thorough regression testing, software developers can ensure that their products continue to meet the high standards of quality and functionality that users expect.

When and Why Do You Need Both Testing Types?

Regression Testing and Unit Testing are two important types of software testing. Regression testing is necessary when changes are made in the code base, which might affect other software parts. Unit Tests are essential because they help identify any issues with the functions individually before being integrated into the final product. Below are some reasons why you need regression testing and unit testing:

When do you need regression testing?

  • Regression testing is testing that makes sure changes or updates to a software system don’t cause any unintended effects or break anything that used to work.
  • You’ll generally want to do this testing whenever you make any changes, add new features, or bring in new data.

Why do you need unit testing types?

  • To identify any problems with specific code units at an early stage.
  • Help troubleshoot complicated systems by isolating individual components.
  • To make it easier to extend, modify, and refactor code over time without breaking anything.

Unit tests vs. Regression tests – the differences

Okay, let’s break it down! The below table gives you the major differences between these tests.

Unit TestRegression Test
Unit tests are designed to test individual code units, typically at the function or method level.Regression testing involves running a suite of tests to ensure that new code changes don’t adversely affect existing functionality in an application. Read here about –Regression test suite
This is a type of white box testingThis is a type of black box testing
Testers usually execute them before integrating new code into the larger application.Developers generally perform regression testing after integration or deployment.
This test targets the methods and functions.This test targets the end-to-end workflows.
Run for every build.Run every time changes are made
It can be fully automated.It can be manual or automated.

Both types of testing are important and work together to ensure our software is working properly.

Tools and Techniques for Regression and Unit Testing

To reduce the risk of introducing bugs and errors in your code, regression, and unit testing are two methods you should employ. After introducing new changes, regression testing ensures that previously working features still function correctly. On the other hand, unit testing focuses on verifying individual components of your code work as intended. Many great options offer robust functionality and capabilities when it comes to tools for these methods. Some of the top picks include:

For Unit Testing:

  1. NUnit: an open-source unit-testing framework for .NET developers with built-in assertions, extensibility support, and parameterized tests.
  2. JUnit: an open-source unit-testing framework for Java developers
  3. JMockit-an open-source tool for Unit Testing with the collection of tools and API

For Regression Testing:

  1. Testsigma: an NLP-based automation testing platform that lets you automate tests for web, mobile, desktop, and API from the same place. With Testsigma, automating and maintaining tests is as easy as writing sentences in English. Know more about Testsigma here: https://testsigma.com/

  2. Subject7: a cloud-native, codeless test automation platform that integrates all testing procedures in a unified platform.
  3. Cerberus Testing: an open-source and low-code test automation platform. It supports Web, Mobile, API, Desktop, and Database testing.

These tools provide developers with powerful capabilities to automate their regression or unit tests more effectively while significantly improving the efficiency of their workflow.


To summarize, regression and unit tests are essential in software testing to ensure quality and prevent errors. Understanding the differences between regression and unit tests is key to implementing an effective testing strategy that improves the overall quality of the software. Yet, using both types of testing in concurrence with each other will help ensure the code is thoroughly tested. If any issues are found, they will be resolved before they can cause problems for end-users.

Frequently Asked Questions

Are regression tests unit tests?

Regression and unit tests are different. Regression tests ensure that existing functionality works correctly after new changes have been done, whereas unit tests verify that individual units of code work properly in isolation. Unit testing is designed to catch bugs early in development, while regression testing is intended to catch issues introduced during later stages.

Is regression testing black box testing?

Regression testing means re-executing the tests for features that could get impacted due to any new changes in the code. So it’s a Black-Box testing technique.

Which testing comes under unit testing?

Unit tests are very low-level and close to an application’s source. They test individual methods and functions of your software’s classes, components, or modules.


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