ITPEC FE Morning October 2020 Question 49
The figure below shows that the cumulative number of bugs reached the target value, when the number of completed test items was X. Which of the following is an appropriate explanation of the situation shown in this figure?
Explanation
A large number of bugs may still remain — the target count was reached while bugs were being found faster than ever.
Up to X the curve rises more and more steeply: each further batch of test items finds more bugs than the one before. Software that is nearly clean shows the opposite shape, a curve that levels off (the top of the S-shaped reliability growth curve) because fewer new bugs turn up. Reaching the target at X only says that many bugs have been found so far; the steep slope says the discovery rate has not started to fall, so many bugs are probably still inside and testing should go on.
Answer (a)
Why not others:
- •(b) — thorough desk-checking and simulation would remove bugs before testing, which would show as a curve that levels off, not one that keeps steepening
- •(c) — the discovery rate is still rising at X, so a count reaching its target says nothing reassuring about bugs after shipping
- •(d) — testing can be judged complete when the curve converges; here the slope is still increasing
Key rule: Judge test progress by the shape of the cumulative bug curve, not by hitting a target count: only a curve that has levelled off suggests that few bugs remain.
System Development Technology · AI-written, may contain errors
This question comes from an official ITPEC past paper. ITPEC Practice is an independent study tool and is not affiliated with ITPEC. See the official FE past-paper collection or Report an issue.