Functional Testing VS. Regression Testing

Functional testing is a practice that increases communication between test managers, test engineers, developers, and business analysts. The management can observe the progress of a project at any time by examining the functional tests. Eventually, this speeds the development processes because well-communicated requirements ensure faster releases. Functional tests also drive architecture with subsystems that have clearly stated responsibilities. A functional testing company follows an approach that evaluates all functions of applications to ensure all components operate according to the requirements.  Each function of the application is tested in-depth to verify that the output by each feature is as desired. Functional testers test all functions by feeding input and verifying the output to check how the system works. It may also involve checking the APIs, database, user interface, security, and functionality of the application under test (AUT). functional tests do not include factors such as structure, code, performance, and environmental factors.  The primary purpose is to ensure the usability and accessibility of the functions as per the required specifications. It also verifies that an application will function properly for all the users.

Testing teams need to include functional and regression into their QA strategies. Functional testing should be a continuous process during the development lifecycle and through production. It aims at ensuring:

• Meeting the end-user requirements 
• App development goals are achieved
• Identification of incorrect specifications
• Looks for interface errors
• Fine more issues 
• Meeting the regulatory and compliance requirements 

Regression Testing 

This type ensures the existing things work after the new changes have been made to the code. It is a regular part of the software development process and is carried out by QA experts. Coders/programmers develop test scenarios to check the bits of code after they are written. These are a part of the process. So, before releasing the new version of the product, old test cases are run against new version to ensure the old functionality is intact. Regression tests can also select partially or completely of the checks that have been already executed. It is necessary to run regression tests for the following reasons:

• Changes to the code are made due to changing requirements
• After fixing defects
• When performance issues are resolved 
• Major changes to an application 
• Configuration changes
• When new features are added to an application 
• Patch fixes 

Scope 

Functional tests have a limited scope as it is feature-specific. For instance, if a team builds a car that has a specific navigation system, testers will check that the is able to locate the car on a map and guide the driver to any desired destination. 

On the contrary, regression testing is not feature-specific. It is performed after a bug has been fixed or modifications have been made, or when a new one is added to an existing software application. Let us take the example of the same navigation system as discussed above. If the mechanic has fixed some issues, then regression tests will be performed. Let’s say the navigation feature was not switching on and the mechanic resolved the issue, testers will check that it not only works but also ensure that everything else in the car is working correctly. Regression involves end-to-end testing of a product whereas functional refers to checking if a single feature works. 

Basic Purpose 

Functional aims at testing if a certain thing of the application works. Whereas, regression addresses detailed concerns about a product such as every feature in an application is working fine, if a certain problem in the app is resolved, etc. The basic purpose of both types is different which follows an entirely different approach. 

Acceptance Criteria

Functional testing does not only checks if a feature works, but also if it works the way it is expected to. If a new one is added to an application, it is not only meant to work, but to also work efficiently. This is known as the acceptance criteria of a feature and functional method checks exactly that. 

Regression testing has to consider the acceptance criteria for several things instead of just the single one that was added, updated, or fixed. This happens because when a new one is implemented or a bug is fixed, the fix may affect another component of an application. Thus, the acceptance criteria for that will no longer be fulfilled and this can only be determined if a tester looks at the acceptance criteria for all features that are caused by the change. 

Why Consider Functional and Regression Testing?

QA teams use these checks to ensure the stability of a product. When the regression testing cycle is performed after a change is made in its code and new bugs are identified, the engineers learn how a code change in one component of a product impacts the code in the other parts. It also helps engineers while they develop new features as they know that certain parts of the code depend on the other parts. 

The results from previous evaluations help teams to plan for future cycles and highlight areas that should be tested when something new is added. Regression testing has a wider scope as compared to functional testing processes. However, if a product has gone through different cycles, teams can estimate the impact of change and then plan to check further.