The Blind Spot of a Passing Suite: A Defect Taxonomy by Discovery Method in an Authoritative Records System

Testing literature evaluates a suite by what it catches. This article evaluates one by what it cannot see. This article treats a test suite as a measuring instrument whose blind spot is a structural property rather than an accident, our study classifies every defect recorded during the development of the Catholic Diocese of Mansa Pastoral Management System, which is a sacramental records platform whose registers are, under canon law, the juridical proof of the sacraments, and not by the component in which each defect lived, but by the method that discovered it. Ten discovery methods and four severity classes are defined. Severity is anchored externally in canon law and in the Zambian Data Protection Act rather than by triage judgement, removing the usual circularity from severity coding. The system carries 1,840 automated tests; its guards were additionally subjected to 225 controlled mutations under a protocol naming the test obliged to fail before the guard was removed. Across 44 system defects the continuously executed suite accounts for five, while the methods in which nothing is executed account for 37. Of the recorded 24 defects capable of silently corrupting a canonical register, 22 were invisible to a green suite of over a thousand tests; the two it did catch were both newly introduced and both caught by structural assertions rather than by examples. We characterized six structural blind spots, including a documented, covered and unreachable guard that no coverage instrument could report as absent.