ITPEC FE Morning October 2018 Question 49

Redundant code cannot be detected — a black box test looks only at inputs and outputs, so code that the specification never exercises goes unnoticed.

Black box test cases are derived from the specification, with techniques such as equivalence partitioning and boundary value analysis. The tester never looks at the source, so a block that is never executed, or that does nothing useful, produces no wrong output and stays hidden. Finding it needs a white box view, such as measuring statement coverage.

Answer (a)

Why not others:

• •(b) — test data growing rapidly with the number of branches and modules is a property of white box testing, where the paths through the code drive the test cases
• •(c) — checking whether the necessary parts are executed, in view of the internal structure, is white box testing
• •(d) — instruction (statement) and branch coverage are white box criteria

Key rule: Black box tests find behavior that differs from the specification; anything that concerns the code's structure, such as coverage or dead code, needs a white box test.

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