<Tr> <Td_colspan="2"> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> Black - box testing is a method of software testing that examines the functionality of an application without peering into its internal structures or workings . This method of test can be applied virtually to every level of software testing: unit, integration, system and acceptance . It is sometimes referred to as specification - based testing . </P> <P> Specific knowledge of the application's code, internal structure and programming knowledge in general is not required . The tester is aware of what the software is supposed to do but is not aware of how it does it . For instance, the tester is aware that a particular input returns a certain, invariable output but is not aware of how the software produces the output in the first place . </P>

Black box testing is applicable to which level of testing