Difference between Functional and Non-functional Testing.

As we know that testing is the most important stage in the process of delivery of any application or software as it is only testing which not only validates the quality of an application but also provides an opportunity to the developer to improve its product.

Every application is being developed as per the requirement of customer/client so on the basis of testing, the functionality of application based on these requirements and testing the usability and performance we can distinguish between Functional and Non-functional Testing.

Following are the important differences between Functional Testing and Non-Functional Testing.

Sr. No.KeyFunctional TestingNon-Functional Testing
1DefinitionFunctional testing is the testing in which the basic functionality, operations and actions of the application/software on the basis of requirements provided is done.On other hand during Non-Functional testing is the testing in which the performance or usability and behaviour of software/application is done under different circumstances.
2Nature of testingAs name states Functional testing does the functional verification of application process in which the requirement and corresponding written code has been verified so nature of functional testing is business requirement testing.Non-Functional testing on other hand does the behaviour validation and verification process which examines the expected behaviour of the application based on dynamic inputs provided to the application so nature of non-functional testing is performance testing.
3Testing targetAs mentioned above, Functional testing targets the requirements of customer.On other Non-Functional testing targets the expectations of customer.
4PrerequisiteFor Functional testing check-list of application process and documentation is required.On other hand for Non-Functional testing performance test cases with different scenarios for execution has been developed.
5Stage of testingFunctional testing generally gets performed before compilation of code.While Non-Functional testing is mostly performed after compilation of code.
6Cost to CompanyIn Functional testing cost of finding defects and fixing is less, also return on investment will be high as this testing involved at an early stage.On other hand in case of Non-Functional testing cost of finding and fixing defects is high and also return on investment will be low as this process involves after the development phase