Concepts of Functional Testing

Function can be described as what the system does. Thus, functional testing is the testing carried out on the functionalities of an application under test.  The functions that a system, subsystem or component are to perform may be described in work products such as a requirements specification, use cases, or a functional specification, or they may be undocumented.

Functional tests are based on functions and features (described in documents or understood by the testers) and their interoperability with specific systems, and may be performed at all test levels (e.g., tests for components may be based on a component specification).

Functional testing in simpler definition is a kind of black box testing that is performed to confirm that the functionality of an application or system is behaving as expected. Functional Testing covers both positive testing (validation of valid inputs) and Negative testing (validation that invalid inputs will not be accepted)

Examples of Functional Testing

1. Testing of an Online Course Application system where users can add apply for a new course, edit course registration, submit courses for review and also delete courses
2. Testing on an online booking system to ensure that customers can book materials online and email is sent to the client of a booking.
3. Testing a banking application to ensure that customer records accounts can be created, customer deposits can be captured, customer withdrawals can be captured and also confirming customers cannot withdraw more than their balance (negative testing).