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Functional Testing vs Regression Testing: Main Differences

Functional vs Regression Testing

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Testing has increasingly become a requirement in the software development lifecycle in recent years. The realization that development is no longer a focal point for stakeholders but saving costs by catching defects early in their application makes it necessary to learn different testing types. 

Releasing buggy software is something avoidable, you don’t want to incur costly fixes, erode trust, and harm a company’s reputation.

In this article, we will cover the topic of Functional Testing vs Regression Testing in-depth.

We will discuss what you need to know, including the definition and purpose of Functional Testing and Regression Testing, why and when to use them, and just enough information about both Functional Testing and Regression Testing.

I guarantee you that after finishing reading this article, you’ll have a solid foundation to make informed decisions in your testing processes.

So, let’s get started.


When learning about Software Testing, it’s essential to understand the distinctions between different testing methods. This blog sheds light on two critical types of testing: Functional Testing vs Regression Testing.

  • Functional Testing: A process that verifies the individual functionalities of software to ensure they operate as intended, with a keen focus on user experience and external behavior.

  • Regression Testing: A safeguarding process that ensures recent code alterations or updates do not negatively impact the existing functionalities, thereby preserving the software’s stability throughout its lifecycle.

As you navigate through this blog, you’ll find a detailed exploration of each testing type, their key components, and when and why to use them. We also dive into the benefits of automated testing and recommend some top-notch automation testing tools in the market.

Whether you’re a software tester, a developer, or someone keen on understanding the software testing landscape, this blog aims to equip you with the knowledge to differentiate and effectively implement Functional and Regression Testing in your projects.

What is Functional Testing?

Functional testing is a type of software testing process that ensures all features of a program or software provide the desired output. In simple terms, it’s like checking if a television does what it’s supposed to do – display video, display audio, and power on/off.

In this case, each software functionality is tested to make sure they are working as intended. This involves interacting with user interfaces, security features, databases, and APIs. 

Functional testing does not consider the application or system code’s structure. The focus is on user experience and external behavior. 

Functional testing is significant because it helps identify and fix defects or errors, reduces production risk, and enhances user experience. This testing is very important in matters of compliance with regulatory standards and maintaining the software’s quality, credibility, and reputation. Overall, consider functional testing as a quality assurance step that ensures your systems or software products are reliable.

Key Components of Functional Testing

The functional testing phase is critical in software testing to ensure the system or application components are functioning correctly. Here are the key components of functional testing:

  1. Requirements understanding: Before starting functional testing, knowing the software or application requirements is crucial.
    For instance, you want to test an e-commerce application. The requirements may encompass effective user authentication and product search with filters or sort options that simplify search results processes. In simple terms, know what the software is supposed to do.
  2.  Test cases and scenarios: Create test cases that will address all your system requirements. In this case, have a clear step-by-step guideline on how to perform the tests.
    Let’s say you want to conduct a functional test of a “User Login.” You have to know what happens when a user logs in and where they are redirected. If these functional requirements are not working, it’s clear where fixing should be done.
  3.  Prepare test data: Functional testing requires a range of test data for complete success. Select appropriate data sets for the test, valid and invalid, to check whether the software handles both scenarios as intended.
    In the case of “User Login,” you can have correct and wrong usernames and passwords to check how the application responds.
  4.  Test environment: Set up the testing environment to mirror the production environment. By doing this, it ensures that the software can be able to function as expected across different configurations and environments. 
  5.  Test documentation: It is important to track the progress of the functional testing to ensure all the testing objectives and goals are met. The document must include the testing process, test reports, test plans, and test reports.

A Closer Look at Functional Testing

Functional testing is used for specific purposes at different stages of software development. Here’s when to perform functional testing and the importance of functional testing:

Finding the Best Time for Functional Testing

  1. During development: Functional testing is most beneficial at the early stages of development. It should be parallel with coding. In this case, the developers can write unit tests to ensure each function works correctly. 
  2. System or application testing: Functional testing is an important part of the application or system testing, where all the functionalities are working as required. 
  3. Part of Regression testing: While regression testing is a separate process, functional testing plays a vital role in it. It helps in verifying that the previously tested functionalities are still working correctly even after recent changes in the code, ensuring that the new modifications haven’t introduced any errors or defects.
  4. Integration testing: Components of software are combined during integration testing. Functional testing checks if these integrated parts work correctly.
  5. User Acceptance Testing(UAT): UAT involves functional testing to determine whether the application meets user expectations before being released.

Understanding the Importance of Functional Testing

Functional Testing
  1. Bugs detection: Functional testing helps identify issues related to the functionality of the application, such as unresponsive buttons or default search bars and defects or bugs.
  2. Enhances user experience: By checking that all features, such as buttons and login page, are working as intended, functional testing ensures the user experience is excellent, resulting in high customer retention.
  3. Risk mitigation: Testing all functionalities is important in reducing defects that could slip through production. Functional testing ensures this can be handled in the development phase to avoid the costly post-release fixes.
  4. Ensuring correct functionality: The main goal of functional testing is to ensure the software or application performs as expected, aligning with user expectations and business requirements.

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What is Regression Testing?

Regression testing is an important process in software development that ensures that code changes or updates do not introduce new bugs that can cause effects in production. Its primary role is to ensure the system is reliable and stable throughout its production and software development life cycle.

Furthermore, regression testing runs a suite of pre-existing test cases in a series manner to ensure that the original functionalities are still working as intended. If any errors are detected, it prompts the coders to make the necessary adjustments or corrections. 

In the context of software modifications and updates, regression testing is crucial as it helps developers catch code errors or integration issues early in the development cycle, reducing the time and cost of fixing them in the future when they become difficult or expensive to make changes. This regression testing cycle and process is important in ensuring that software continues to meet the user expectations during its production life.

Key Components of Regression Testing

Regression testing is a requirement in the software development lifecycle that ensures all features work correctly even after making changes to the code. The key components of regression testing include:

  1. Test selection criteria: Regression testing is time-consuming, so it’s necessary to have criteria for selecting a single test case. In simple terms, prioritize which areas of code or frequently used features are more likely to be affected by changes. 
    Consider a banking app. You expect there to be frequent transactions. Test selection criteria may focus on transaction-related tests over less-used features.
  2. Automation tools: Automated regression testing tools such as Selenium and Cypress play a crucial role in running test cases and comparing results. They are efficient in test management, making it easy to track changes made to the software.
  3. Test environment management: DevOps practices such as configuration environment come into play in this case. You would want to maintain identical test environments in the development stages to avoid environment-specific regressions.
    Imagine your web application works fine in the development environment but does work in a production environment because of database configuration differences. With proper test environment management and regression testing, such challenges can not be avoided.
  4. Version control system: A version control system like Git or SVN helps in bug trucking and code changes, making it easier to know when and who made the change. This is important for developers to pinpoint regression effects during regression testing.
  5. Test suite: The test suite contains test cases of different elements of the software’s functionality. These test cases act as references when code changes introduce new issues. The test suite should have the correct information, including manual and automated tests.

A Closer Look at Regression Testing

It’s a question you probably will ask yourself the first time you interact with regression testing. Let’s start with the when.

Finding the Best Time for Regression Testing

  1. Bug fixes: It should be taken up when changes have been done to the code. Regression testing comes in to verify that the changes do not create other problems. 
  2. Code updates: When you make updates to your software, it is necessary to perform regression testing because even a slight change can unintentionally affect other parts. Regression testing ensures that new features do not affect existing ones.
  3. Integration of Third-Parties: When integrating third-party libraries or APIs in your software or application, regression testing helps ensure these components do not cause compatibility issues, especially in future versions.
  4. Environment and platform changes: If you change the database or migrate your system to a new platform, regression tests will be critical to ensure the software continues to function smoothly.
  5. Long-term stability: Over the long term, you would expect your software to accumulate a lot of code changes. Continuous regression testing helps maintain the functionality and quality of the software. 

Understanding the Importance of Regression Testing

Regression Testing
  1. Preserve existing functionality: Regression testing ensures existing functionalities continue to work as intended. This is essential for maintaining consistency and user satisfaction.
  2. Detecting defects: Regression testing can also be used to check the side effects that code changes may cause. These defects could go unnoticed, leading to serious problems affecting user experience.
  3. Saving time and resources: You can save time and resources if you automate regression testing. This is more efficient than manual testing, especially when dealing with complex tasks. 
  4. Compliance requirements: Industries have strict requirements mandating regression testing. Regression testing will help you meet regulatory standards and ensure any changes align with the industry regulations.
  5. Enhancing collaboration: Testing teams and developers can build a constructive and lasting relationship. This helps in creating a culture of focusing on quality and accountability within the development phase and production lifecycle.

Differences and Similarities: Functional Testing vs Regression Testing

Let’s now start to understand the differences and similarities between Functional and Regression Testing in the simple table below:


Functional Testing

Regression Testing


Verifying whether all the functionalities of the software are working as intended.

Ensures the recent code changes do not cause issues with the existing functionalities of the software.


Focuses on specific functionalities of the application.

Verifying unintended side effects of code changes 


Conducted once – during new feature release or update

Execution is often – after code changes


Checks whether the software meets desired  feature specific user requirements and specifications.

Ensures new code changes do not affect existing functionalities.


Has a higher manual testing component but can also be automated.

Heavily automated to validate the entire software or application.

Test data

Requires predefined test data.

Uses a combination of existing and new data.

Test phases

Usually takes place in the development phases when features are added.

Continuous process triggered by code updates.

Overall, functional testing and regression testing are reliable and effective for delivering bug-free and user-satisfaction software, but they are different because they are executed at different stages of development.

Benefits of Automated Testing

Automated testing has benefits that streamline and enhance the testing process, making it a better option compared to manual testing methods.

Automation speeds up testing cycles. Automated test scripts can be executed at high speeds and in big volumes quickly. This speed is necessary as it enables you to get quicker feedback and effective testing. Also, the speed is what you want for repetitive tests. 

Automation is also consistent. It reduces the risk of getting negative test results. Human testers may unintentionally introduce errors, while automated tests have already been predefined to follow specific scripts.

Moreover, automation enhances test coverage, where automated tests can handle a wide range of configurations that would be almost impossible for manual testers to cover comprehensively. This helps to identify errors early, reducing the time and cost of fixing issues later.

Automation also aids in regression testing, where the previous existing functionalities are rechecked to verify if they are still working as expected because any kind of change can cause new problems. 

Overall, automated testing is a valuable tool for software development, improving the stability and quality of the product and maintaining user satisfaction. 

Top Recommendations for Effective Testing Tools

There are several effective functional testing and regression testing tools. Here are some top recommendations:

  1. Selenium: It is an open-source tool that is widely known for its efficiency automation in web applications. You can use your favorable language using this tool.
  2. Appium: It is an open-source tool useful for mobile automation applications on iOS and Android. As a tester, you can use your preferred programming language using this tool.
  3. Playwright: It is a powerful open-source automation framework used for browser automation and end-to-end testing. It allows testers to automate interactions with different web browsers like Firefox, Webkit, and Chromium.
  4. Supertest: It is a JavaScript library for testing HTTP APIs, including GraphQL and RESTful APIs.
  5. Test Sigma: It is a cloud-based test automation platform designed for mobile and web application testing. This tool simplifies creating, managing, and executing automated test scripts.

Frequently Asked Questions

Regression testing is one of the types of testing that encompasses the functional testing processes, primarily focusing on ensuring recent changes do not affect existing functionalities. Functional testing is the overall testing of the application’s functions or features to ensure they work based on intended specifications. In simple terms, regression testing is a fixated aspect of functional testing that ensures old features continue working even when there are new additions.

There are several factors to consider to ensure regression testing is effective. First, you have to consider having the right test cases. You should focus on using test cases that cover frequently used functionalities of the software. Test environments must act as mirrors of the production environment, including configurations, data, and software. Also, clear documentation and collaboration are vital for regression testing. Finally, proper tracking during regression testing helps to ensure critical features are addressed promptly. 

Regression testing is performed after functional and smoke tests. The approach is important in maintaining software quality in the testing process. Smoke testing is performed after the software is built to check whether the features are working correctly. It is helpful in preventing flawed functionalities from progressing further in the development stages. 

After smoke testing, functional testing is then conducted to evaluate the software’s functionalities based on predefined requirements. Once functional testing is complete, regression testing is performed to ensure that changes made to code or features do not affect previously tested functionalities. It helps solve unintended effects and maintain the existing system's efficiency.

Regression bugs and defects discovered using functional testing are not the same, although they show issues that are in the software.

Regression bugs are a result of recent code changes. They occur when the updates made unintentionally affect existing or previously functioning features. Remember, these bugs are not in the stable version of the software. 

On the other hand, defects identified in functional testing include inconsistencies, errors, or unintended behavior of the software’s features. These defects probably existed in the software before changes, but it is not limited to regression testing. In essence, both impact the software’s quality and stability, though their focus and origin are not the same.


It is evident that both functional testing and regression testing are important in ensuring software stability and quality. Functional testing is helpful in examining the software’s functionalities or features to ensure they are working correctly and can satisfy the customers. Conversely, regression testing ensures that previously tested functionalities remain intact despite new changes. 

Together, functional testing and regression testing offer the quality assurance you want for your system. Functional testing ensures the software features are working, and the regression tests act as a guardian, ensuring the changes do not affect the functionality. Both are vital for delivering working software.

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If you have any questions or comments, feel free to leave them in the comments section below.

Thanks for reading, and we look forward to seeing you in the next post!

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