For software applications, functional testing is defined as testing performed to test the core functions of an application. For example, functional test cases for the WhatsApp application will be all the features that WhatsApp is providing, like creating and sending messages in all formats and other features related to groups. In other words, all the features which a user can see or work with will be considered functional, and testing the same will be considered functional testing.
Non-functional testing is performed for safeguarding the application. Safeguard here is not used in the same context, but concerning the software applications. If I say, all the features of the application that a user expects to have but cannot test directly. Like user does not expect that his/her WhatsApp is hacked, but there is no way for a normal user to test it. Similarly, when they click on the WhatsApp icon, they do not want the application to take ages to open. To ensure the best user experience in terms of performance and security, the software testing field has to offer a wide range of non-functional testing techniques.
As a software tester, whenever you are tasked to plan for a test strategy, both functional and non-functional should be incorporated. For a QA engineer, it is very important to understand the difference between functional and non-functional testing. This will help streamline the testing efforts, and test planning, and help prioritize the test cases.
Here are some key differences between functional and non-functional testing:
- Purpose: Functional testing verifies that the software functions as expected, while non-functional testing verifies that the software meets non-functional requirements such as performance, security, and usability.
- Scope: Functional testing focuses on testing the features and functions of the software, while non-functional testing focuses on testing the non-functional aspects of the software.
- Testing techniques: Functional testing is typically done using techniques such as black-box testing, while non-functional testing may require different techniques such as white-box testing, performance testing, or security testing.
- Test cases: Functional testing requires test cases that cover all the features and functions of the software, while non-functional testing requires test cases that cover specific non-functional requirements such as performance, scalability, or security.
In summary, functional testing verifies the functional requirements of the software, while non-functional testing verifies the non-functional requirements of the software. Both types of testing are essential for ensuring that the software meets the needs and expectations of its users.