Definition

A test for behaviour viewed from the exterior of the product under test, such as some user-accessible feature.

[Source: BCS]

Comment

Black box tests are where tests are designed based on no knowledge of the internal structure of the component. (As opposed to white box testing during which testing is based on some understanding of the internals of the product under test).

Black box tests are a better regression test from a business perspective than white box tests.

Also see: Functional testing, Non functional testing, White box test