Definition

A white box test assumes an understanding of the internals of the product under test. Contrast with black box testing, which is a test for functionality that may be viewed from the exterior of the product under test, such as some user-accessible feature.

[Source: BCS]

Comment

White Box tests are essential for ensuring that the system internals are performing correctly. White box testing is sometimes called ‘glass box testing’ or ‘clear box testing’ or ‘structural testing’.

Understanding the internals of a system enables testers to forecast more easily where defects are likely to be found. It is thus easier identifying equivalence classes and to minimise the number of ‘duplicate’ tests. This approach focuses on the ‘how it works’ as well as the ‘what it does’.

Also see: Black box test