Functional Vs Regression Testing: The Key Differences to Know

functional vs regression testing

Testing is frequently overlooked or not given the same importance as development in the software development lifecycle. 

However, it is just as crucial as development because a buggy application with multiple features can cost you money and a user base.

In this blog, we’ll cover in detail the topic of Functional vs Regression Testing.

We will discuss everything you need to know in this blog, an entire blog including the difference between Regression Testing and Functional Testing, along with the excellent amount of information about both Regression Testing and Functional Testing. 

So, let’s get this party started. 

Functional vs Regression Testing: Definition, Importance, and Types

Before going comparison part of regression and functional testing, let’s discuss definition, their needs and various types.

What Is Functional Testing?

Functional testing is a software testing approach that evaluates all of the software’s features/functions to ensure that each component meets the required specifications. 

Each application function or piece is thoroughly tested to ensure that the output/result provided by each application function is as expected.

Function functions are tested by feeding input and verifying output to check what the system does. APIs, databases, security, user interfaces, client/server applications, and the functionality of the Application Under Test are all checked during the testing. 

Functional testing does not usually consider internal structure, code, performance, or environmental factors.

The primary aim of functional testing is to ensure Usability, accessibility, and compliance with requirement specifications. In addition, it provides that a product or application will work correctly and efficiently for users.

Know more about Functional Testing; Unpacking the Concept

What do you test in Functional Testing?

Mainline functions: Test an application’s primary functions.

Basic Usability entails testing the system’s Usability on a fundamental level. For example, it determines whether a user can freely navigate the screens without difficulty.

Accessibility: Verifies that the system is accessible to the user.

Testing Techniques to Check for Error Conditions: Using testing techniques to check for error conditions. It examines whether the appropriate error messages are displayed.

To ensure the validity of the functionality of an application program, functional testing employs a black box testing approach. Because the emphasis is on functionality, the design and user experience aspects are unaffected. The following are the main aspects of functional testing.

Analyze Needs of the Customer:

  • Validation of the input data
  • Getting the expected outcomes
  • Execution of the test case
  • Comparison of the actual and anticipated outcomes
  • Comparing the results of the test cases

Why Do You Need To Perform Functional Testing?

The importance of functional testing in validating the quality and functionality of the software cannot be overstated. 

Quality assurance teams use this software testing technique to verify software functionality based on the Software Requirements Specification (SRS) and ensure the system functions according to user specifications.

This type of testing aids in determining whether the system is ready for release and error-free. This testing does not rely on assumptions about the system’s structure, but it ensures that a high-quality product is delivered. 

Essentially, this testing method is used to test usability features, specific error conditions, accessibility features, and other essential software functions.

It is very easy to dismiss software testing as a waste of time and money. However, a minor bug spiraled out of control for so many organizations. Embarrassing software flaws in a product may cause a brand to go viral but in the wrong way. 

There is no need to learn the importance of proper software testing techniques the hard way.

Best Practices For Functional Testing: 

#01 Plan Of Testing And Test Cases

The goals and scope of testing, the number of people who will be involved in the testing, the hardware, and software tools that will be used in the testing, the testing schedule, and the number of test cases that will be written to perform the testing are all part of the planning process. 

The input data for test cases are based on the functionality’s specification. These test cases should be organized and prioritized to reduce delay and risk. Finally, the development team should review these test plans.

#02 Execution Of Test Cases Should Be Well-Planned.

Testing specific workflows in your app is known as test execution. Functional testing depends heavily on this. 

Your testers can use test execution to work their way through specific functions for your mobile or web app, ensuring that they work as they should within the pre-planned workflow.

Assume you’ve created a test case for your e-commerce app. You want users to be able to search for red trainers,’ click on a specific pair, add it to their shopping bag, and check out. Within each step, testers will test specific functions such as the search bar, card payment, and shopping bag to see if the expected results are obtained.

#03 Reporting Of Test Results

A test result report follows a specific format and includes a summary of all test cases completed, the time spent at each stage for each feature, and its status and progress. 

It also contains information about any new defects discovered during testing.

Overall, the test result report should be presented clearly and simply so that the development team can understand it.

#04 Automating Functional Testing

Automated testing improves the product or software’s quality while also saving time. What should be automated is up to the tester to decide.

Automated testing is slightly more expensive in the short term, but it is more beneficial to the product in the long run. Avoid automating things that can be done more cheaply and effectively by manual testing.

#05 Manage Defects With Data Storage System

Many people working on the same functionality may result in duplicate defect reports, incorrect order of issue resolution, consideration of incorrect defects, and other issues. A centralized data storage system that everyone can access should be managed to prevent this.

The system includes standard templates for defect reporting and verification, a priority ranking of defects, and information about task assignments; this aids in the solution of problems one at a time.

#06 Collect Data Required To Perform Testing

It is critical to understand what will be tested and the testing plan or procedure. The development team is aware of essential user commands and processes. Collect the data and test the most important aspects first.

For product development, it is critical to be aware of market demands. For example, a document or matrix should be created to connect the product to the requirements and test cases. Matrices should be updated to reflect changes in conditions.

Different Functional Testing techniques:

End-user-based tests: In this functional testing technique, the system is tested to determine whether or not all of the components work perfectly together.

  • Equivalence tests: The test data is divided into various partitions in this equivalence test technique, and the data in each partition must respond similarly. Thus, tests are run on a single condition; if any of the conditions in any partition fails, the others stop working.
  • Boundary value tests: This technique helps validate how the system performs when boundary data limits are used. In most cases, if the provided inputs are less than the boundary values, the test is considered harmful.
  • Decision-based tests: This decision-based testing technique aids in validating the possible outcomes that can be obtained when a specific condition is met.
  • Ad-hoc tests: This testing technique aids in identifying bugs that were missed in previous tests. Ad-hoc testing is an effective method for identifying bugs that were not previously identified.

What is Regression Testing?

Regression testing is the type of testing which ensures that changes made to the codebase do not affect existing software functionality. These code changes could include, for example, adding new features, fixing bugs, or updating a current feature.’

In other words, regression testing entails re-running previously cleared test cases against the new version to ensure that the app’s functionalities are working properly. Furthermore, regression testing is a series of tests, not a single test run whenever new code is added.

Coders create test scenarios and exercise to put newly written code to the test. These tests are included in the ‘test bucket.’ 

Before releasing a new product version, old test cases are run against the new version to ensure that the old functionality remains intact. This is because adding new code can sometimes introduce errors in the existing code.

Regression Testing frequently entails selecting a subset of all previously executed tests to run again.

  • Because of changing requirements, the code has been modified.
  • Software is updated with new features.
  • Following the correction of defects.
  • Patch to address a performance issue.
  • Significant modifications.
  • Configuration changes.

When To Perform Regression Testing?

It should be taken up when new functionality is introduced: It’s one of the most crucial steps in the regression testing procedure. 

When developers submit new code, they don’t always pay attention to how it interacts with existing code, so software regression testing should be used to identify any potential problems.

Existing functionality has been altered based on the requirements, and developers may revise existing functionality and exclude/edit some features during the agile software development process. 

In such cases, the functionality and regression testing process determines whether or not the new changes have harmed the rest of the functionality.

New Integration on Other Products: Regression testing ensures that the software product continues to perform flawlessly even after integration with another product.

Why Regression Testing Is Important?

#01 Makes sure that new coding does not interfere with existing coding features

Regression testing is also necessary to ensure that any new code or program updates to software do not interfere with the current features dictated by older code. 

For example, when a program or application is updated, software developers typically use regression testing to assess the viability of new features and ensure that the new features do not distort the program’s existing features.

#02 The functionality of the new programming code is evaluated.

Regression testing is an essential tool for determining the success of incorporating new code into an existing program or application. 

This is because regression testing is used to test a software program before implementing new coding and then retest the same software to ensure that the application retains its functionality even after new coding is introduced.

#03 Ensures that no defects or bugs remain after software updates have been implemented.

Regression testing can also be used in quality assurance assessments by developers to check for any adverse side effects in the software. 

For example, a video game developer, for example, might use regression testing to evaluate any issues, bugs, or glitches that arise after introducing new gaming code into an application. So, for example, suppose there are any bugs or issues with the program. 

In that case, the developer can make the necessary changes before retesting the application to ensure that the problems have been resolved.

#04 Allows for the retesting of existing software following application changes.

Regression testing is also vital for providing additional test executions to ensure the viability of program code changes. Retesting each case following a software update or modification enables developers to assess how the new changes affect the program.

For example, suppose a software developer tests a software program after initializing new program codes and discovers that the new features disabled existing features. 

In that case, the developer may retest the update each time they make a repair or change to it. Retesting allows the developer to pinpoint the source of the problem and reconfigure the program to run at peak performance.

Regression Testing Tools:

Developers can choose which tools to use to successfully execute the process after selecting test cases to perform regression testing on. Common regression testing tools can include the following, depending on the project:

Functional regression testing tools enable developers to test individual software program elements for errors or defects and generate a report to aid future development.

API testing tools: API testing, also known as application program interfaces, allows developers to set input criteria to ensure that the software’s output meets performance expectations.

Unit regression testing tools enable developers to evaluate specific code elements within a software program to ensure the highest quality and functionality of each code that is integrated into the application.

Challenges of Regression Testing:

When starting regression tests, several challenges may arise. For example, depending on the test case, it can be challenging to start regression testing every time a program changes while staying within the project scope and budget. 

Furthermore, continuous regression testing can create large test suites that require more resources to complete on time.

A database is created during each test case to store all data related to that test case. In addition, consistent regression testing can necessitate the generation of large amounts of data, resulting in ever-expanding test suites. 

This factor may challenge regression testing entire test suites depending on the project budget and scope. Outlining the frequency with which to perform regression testing can also be challenging. 

For example, developers may choose to perform regression testing every time software modifications are integrated or only after errors or defects are repaired. 

However, building large test suites can necessitate additional resources, and frequent regression testing can also require additional resources.

Best Practices For Regression Testing:

#01 Understanding The Testing Scope

Before beginning the regression testing process, it is critical to understand its scope because each testing project differs in scope, time, and goals. 

Understanding the differences in scope will allow you to better plan the execution of your regression cycle.

#02 Automate The Appropriate Test Cases

Automation only gives you a competitive advantage if you use it correctly. So, first, you must determine which test cases can be automated and which cannot. 

Then, automating appropriate test cases will boost your productivity and save you time.

#03 Monitor ROI

The return on investment (RoI) is the most important metric for determining the success of your regression testing campaign. 

QA teams should continuously track RoI using advanced analytics and reports generated by automation tools. It will assist you in seeing the reality on the ground and areas that require improvement.

#04 Giving Test Cases A Grade

If you want to succeed with regression testing, you must grade all of your test cases. Then, you should compare and track their business impact on different platforms and then prioritize various test scenarios based on those evaluations. 

This will assist you in understanding, differentiating, and identifying multiple roadblocks and conducting effective testing based on the requirements.

#05 Keeping Up With the Most Recent Regression Suite

You must also keep up with the latest regression testing suites, just as with any other technology. Always consider both functional and non-functional requirements for this purpose. The QA team should always execute the suite’s high-priority and high-value test cases first.

#06 Hands-On Knowledge Of Every Change

If you work in software development, you must be aware that the only constant changes. As a result, having hands-on knowledge of each modification is required.

#07 Maintain Regular Communication 

Regular communication between developers and testers to stay up to date on the latest upgraded version and be aware of any immediate changes. They can plan their testing ahead of time to stay on schedule for the app or product release.

Difference Between Functional Testing And Regression Testing

#01 Feasibility of Automation

Functional testing is performed manually at first, and once a feature is stable, test cases are automated. However, only those test cases that are already stable are executed manually or automatically during regression testing, so this can be automated when needed.

#02 Maintenance/Modification Of Test Script

Because functional test cases are few and focused on a single feature, they do not require extensive modification.

Test scripts in the regression suite, on the other hand, require more maintenance because the test suite is designed to test overall functionality. 

However, there is a possibility that it contains old test cases. In addition, functionalities that have changed, new features that have been added, or some features that have been removed may be included in test cases. 

#03 The Goal Of Testing

Functional testing determines how closely the developed application matches the desired requirements. 

The purpose of regression testing, on the other hand, is to ensure that any changes to the application or systems have not resulted in code breaks and that the system continues to function properly.

#04 Test Case Executed

The functional testing test suite includes a new set of cases and functionalities that have never been tested or executed before. The test cases are re-executed when a defect is raised against a requirement. 

Following that, it is fixed and assigned for retesting. If the fault is closed during retesting, the previously failed linked test cases pass. Cases that have previously been tested and passed are included in the regression suite.

Regression testing entails re-running test cases to ensure that changes have not affected previously tested features.

#05 Scope of Testing 

Because functional testing is feature-specific, it has a limited scope. For example, suppose a team creates a car with a specific navigation feature. In that case, testers will ensure that the quality can locate the vehicle on a map and guide the driver to any desired destination.

Regression testing, on the other hand, is not feature-specific. It is carried out after a bug has been fixed, changes to a feature have been made, or a new feature added to an existing software application. So let’s look at the same navigation feature we discussed earlier. 

Regression testing will be carried out if the mechanic has resolved some issues. If, for example, the navigation feature was not turning on and the mechanic fixed the problem, testers will ensure that it works and that everything else in the car works properly. 

Regression testing entails testing a product from beginning to end, whereas functional testing is concerned with determining whether or not a single feature works.

#06 Acceptance Criteria

Functional testing determines whether or not a feature works and whether or not it works as expected. 

When a new feature is added to an application, it is supposed to work and is also supposed to work efficiently. This is known as a feature’s acceptance criteria, and functional testing is used to test that feature.

Regression testing has to consider the acceptance criteria for several features instead of just the single added, updated, or fixed element. 

This happens because when a new feature is implemented, or a bug is fixed, the fix may affect another component of an application. 

Thus, the acceptance criteria for that feature will no longer be fulfilled, and this can only be determined if a tester looks at the acceptance criteria for all features caused by the change. 

Read Also: Sanity Testing Vs Regression Testing


To ensure a product’s stability, QA teams use functional testing and regression testing. 

When the regression testing cycle is run after a change is made to the code and new bugs are discovered, the test engineers learn how a code change in one component of a product affects the code in the other components. 

It also aids engineers in developing new features because they are aware that certain parts of the code rely on others.

Not when bugs are fixed, but when new features are implemented, it is critical for teams that are still figuring out which features rely on each other to deliver a functioning product. 

Previous test results assist teams in planning future testing cycles and highlighting areas that should be tested when a new feature is added. When compared to functional testing processes, regression testing has a broader scope. 

However, if a product has gone through multiple cycles, teams can estimate the impact of change and plan further testing.

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