Functional testing validates the software system against the functional requirements/specifications. Functional testing aims to test each function of the software application by providing appropriate input and verifying the output against the functional requirements. It involves black box testing and is not concerned about the application’s source code. Each system functionality is tested by providing appropriate inputs and verifying the output. It involves a series of tests that perform a feature-by-feature validation of behavior using a wide range of normal and erroneous input data.