Difference Between Regression Testing vs Functional Testing

Difference Between Regression Testing vs Functional Testing: Regression Testing vs. Functional Testing is one of the most important questions you have to answer as a tester. The answer determines your testing methodology and how you organize your tests and test cases. There are plenty of articles written on this topic, comparing various approaches but most of them don’t provide an easy-to-understand visual which can help both parties involved in deciding which track to take – management or QA.

This article answers this need by providing two separate charts showing the difference between regression testing and functional testing through simple pictorial representation. We will be discussing these in detail below:

Regression Testing

Regression Testing is a process of validating enhancements and modifications made to the software. Regression testing determines whether newly added or modified code changes have broken any existing features in the previous release. It involves re-testing previously executed tests on new build/s and comparing results with the previous build/s. The goal is to verify that old functionalities are still working as expected after changes have been introduced to the application.

Functional Testing

Functional Testing is an automated process of validating functionality across a range of user inputs. Functional testing determines whether the application works as documented, i.e. in accordance with the design specifications and intended business function for which it was meant. It involves executing all tests cases defined for complete feature or product under test, with single/multiple data sets. The goal is to verify that functionalities are working as per design expectations.

Functional testing is more of a scientific approach to software testing. It involves the execution of defined test cases with defined data sets, designed for specific functionality (e.g. login), across different GUI/web pages and other components within the application under test. If anything goes wrong, it highlights a defect (bug) in the code, which needs to be fixed in order to produce appropriate expected results. Functional testing does not provide any information about how the application behaves when new code/s are added, or when existing code is modified.

Difference Between Regression Testing vs Functional Testing

We can now understand the difference between the two approaches/methodologies in simple pictorial representation below:

Regression Testing

• It is a process of validating enhancements and modifications made to the software.
• It involves re-testing previously executed tests on new build/s and comparing results with previous builds.
• The goal is to verify that old functionalities are still working as expected after changes have been introduced to the application.
• It helps verify that the application is still working as expected after changes have been introduced.
• It provides good information about code changes, but not much about the business/functional behavior of the application.
• It is a costly process as it requires executing all old test cases again, on newer builds.
• It can be automated to some level, but most of it needs to be executed manually.
• It is a backward approach.

Functional Testing

• It is an automated process of validating functionality across a range of user inputs.
• It involves executing all tests cases defined for complete feature or product under test, with single/multiple data sets.
• The goal is to verify that functionalities are working as per design expectations.
• It helps validate that application is performing functions as documented for a particular feature.
• It is easier to automate and run tests through GUI with no human interference (for scenarios without user interface).
• The goal in this case is to verify which button(s) were pressed, when and why.
• This method also helps validate whether the application behaves as expected after changes are done to it.
• It provides good information about the business behavior of the application.
• It is an ideal approach for regression testing as well as functional test automation.