A test of behavior based on the system specifications or functionality. Black-box testing does not use knowledge of the internal structure of the system, but only checks the system conforms with the expected behavior which is visible externally.
Black box testing traditionally has involved testing a system as a whole; however, with the advent of multi-tiered systems
, black box testing has come to also refer to testing tiers or components of a total system since those tiers are often entire systems unto themselves with only loose ties to the other tiers of the system. Tests that focus on a specific tier can determine whether the detected Bottleneck
resides in that tier only. Black box tests generally do not identify of the specific Bottleneck
. Instead, diagnostics must be performed on the tier while generating a load to find the actual Bottleneck
As a contrast see also White-Box Testing