During testing, a reliability growth curve was plotted with the test time (or the number of test cases executed) on the horizontal axis and the cumulative number of defects found on the vertical axis. The curve is still rising, with no sign of saturating (leveling off). Which judgment is most appropriate?

Answer: C. Many undiscovered defects are probably still present, so testing should continue and the defect trends should also be analyzed

As testing progresses, defects are found one after another at first, and fewer are found as the remaining ones decrease, so the cumulative curve becomes S-shaped (approximated by a Gompertz or logistic curve) and eventually saturates. A curve approaching saturation is a sign that quality is stabilizing, but while it keeps rising, many defects are probably still present. Having executed the planned test cases is not, by itself, a reason to end testing. The curve is fitted to estimate the number of remaining defects, which is used to add or focus tests.

• A. Defects still being found shows that many remain, which is no reason to end testing.
• B. How close the curve is to saturating is an important indicator of whether quality is stabilizing.
• C. Correct. While the curve has not saturated, many defects are assumed to remain, so testing continues.