Functional testing is black-box type of testing geared to functional requirements of an application. Test engineers *should* perform functional testing.

Functional testing is the same as black box testing. Black box testing a type of testing that considers only externally visible behavior. Black box testing considers neither the code itself, nor the "inner workings" of the software.

Function testing is a testing process that is black-box in nature. It is aimed at examining the overall functionality of the product. It usually includes testing of all the interfaces and should therefore involve the clients in the process. Because every aspect of the software system is being tested, the specifications for this test should be very detailed describing who, where, when and how will conduct the tests and what exactly will be tested.

The portion of the testing that will involve the clients is usually conducted as an alpha test where the developers closely monitor how the clients use the system. They take notes on what needs to be improved.