Functional Testing and Non-Functional Testing
Whether it is software, application or website development, the role of software testing is of paramount importance to attain defect-free and smooth running of products. It is a process that checks the quality of the product to find whether the developed software or application meets the specified requirements or not. Apart from quality, testing can also remove most of the bugs and errors from the software.
Software Testing is mainly classified as Functional Testing and Non-functional Testing, which have their distinct advantages, benefits, and features.
Functional Testing
- Functional testing verifies the ‘Functionality’ of the software or application under test. It ensures that each function of a product operates in conformance with the requirement specification. In this type of testing, the software is tested for the real environment, and it is not concerned with the source code of software or application. Functional testing is carried to describe the behaviour and execution of the software system.
- Before performing the Non-functional test, it is important to conduct Functional Testing to efficiently understanding how the system executes its function. ‘Functionality’ of the software or application is tested by giving proper input and comparing actual results with expected results. Being automated or manual involves testing APIs, Databases, User interfaces, and functionality of a product.
Non-Functional Testing
- Non-functional testing verifies the non-functional aspects like usability, reliability, performance of software or application. It focuses on all the aspects which are not addressed in the functional testing. When a product runs as per the consumer’s expectation and is efficient under any circumstances, then it is considered a reliable product. Non-functional testing is carried under these parameters of customer experience. It is a crucial factor in satisfying the client’s expectations. As it’s not feasible to carry Non-functional testing manually, some special automated tools are used in this type of testing.
Head to Head Comparison between Functional and Non-Functional Testing (Infographics)
Below are the top 10 differences between Functional testing vs Non-functional testing
Key Differences between Functional and Non-Functional Testing
Let us discuss some of the major differences between Functional testing vs Non-functional testing:
1. Motive
The objectives for which each of these is used are very different. Functional testing is used to verify the demands and requirements that the system is supposed to meet are met correctly. It is used to check that the software application does not have any bugs and aids in the decision-making about the release and promotion of it. On the contrary, non-functional testing’s objective is to see if the application performs as the customer expects it by examining the user experience. In this, response time to perform the tasks or to the customer’s request is also assessed.
2. Testing Techniques/Sub-tests
The functional and non-functional aspects of the software are checked by performing a variety of tests. Under functional testing, the sub-tests performed include unit testing for checking errors and bugs from the initial stage of developing the application, smoke and sanity test for ensuring the software works as per the given specifications, white-box test for the examination of code, black-box test by running test cases on the system, integration test for checking that all components interact as they are expected to with each other, etc. While for non-functional testing, it is checked by performing a performance test for quality, load test for behaviour under normal as well as extreme conditions, compatibility test, configuration test, test for stress to check its limits, security test, scalability test, recovery test to check for the duration of recovery in case of failure or crash, and more. These are commonly done sub-tests but can vary from system to system.
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3. Criteria for Testing
There are several criteria based on which functional and non-function testing are assessed. For functional, there are positive as well as negative parameters. Functional tests are performed using manual and automated tools. The testers feed valid and invalid inputs to the application and see if the outputs generated meet are what is expected. Invalid inputs help understand the performance of the system in unexpected situations. After checking whether the system gives desired outputs, the functional test is considered to pass or fail. This is very different from the parameters to be considered while performing the non-functional testing.
4. Bugs, Errors, and Defects
Functional testing involves assessing for functionality and features. If bugs or defects infiltrate the system, this is measuredly affected. The software is checked for these at every step under functional testing in the software development life cycle. However, there is no need to test for bugs, faults, or errors while testing the system for non-functional requirements. The system’s behaviour under several different conditions, the response time, and user experience are analyzed under non-functional testing.
Functional Testing vs Non-Functional Testing Comparison Table
Let us discuss the topmost differences between Functional testing vs Non-functional testing.
| Parameter | Functional Testing | Non-Functional Testing |
| Objective | Validate software actions. | Validate the performance |
| Usage | Verifies the behaviour of the application | Verifies the performance of the application. |
| Execution | Carried out before non-functional testing. | Carried out after non-functional testing. |
| Requirement | Easy to define functional requirements | Difficult to define the requirements for non-functional testing |
| Focus area | Client’s requirements | Client’s Expectations |
| Manual testing | easy to execute | Difficult to execute |
| Requirements | functional specifications | Performance specifications |
| Example Test Case | Check Login Functionality
|
Checking how many people can simultaneously login into software. |
| Functionality | Describe what the software does | Describe how the product works |
| Testing Types | Examples of Functional Testing Types
Smoke testing Globalization User Acceptance Unit testing Regression testing Integration Testing Localization
|
Examples of Non-functional Testing Types
Performance Testing Portability Testing Compliance Testing Scalability Load Testing Disaster Recovery Testing |
Conclusion
Through this article, we have explored and understood what functional and non-functional testing is. Looking at the comparison and differences between functional vs non-functional testing, it is understood that these are strikingly distinctive but equally important. There are different ways and strategies for performing both. It is important to provide the requirements and specifications of the system as well as the client expectations beforehand to make it easy for the testers to conduct these tests. Before launching the software, it is necessary to properly examine whether it meets both functional and non-functional needs.
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