ITPEC IP October 2023 Question 49
Which of the following is the appropriate description concerning the black box test?
Explanation
Focusing on the input and the output — a black box test treats the program as a box whose inside is not looked at, and checks its outputs against the specification.
Black box test cases are derived from the external specification: which inputs the program accepts and what it must output. Typical techniques are equivalence partitioning, boundary value analysis and decision tables. The tester does not need the source code, and the test finds functions that are missing or behave differently from the specification.
A white box test is the opposite: it is designed from the internal structure (the source code) and measured by coverage, such as statement coverage (every instruction executed) and branch coverage (every branch taken).
Answer (d)
Why not others:
- •(a) — testing every branch is branch (decision) coverage, a white box criterion
- •(b) — executing every instruction is statement coverage, also a white box criterion
- •(c) — basing the test on the program's internal structure is the definition of the white box test
Key rule: Black box tests are designed from the specification and cannot show untested paths; white box tests are designed from the code and cannot show missing functions, so both are used.
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