mutation-equivalent-in-architecturelisted

Use when a mutation-testing campaign produces a surviving mutant that LOOKS like a genuine test-coverage gap but cannot be killed by ANY falsifiable test in the current code architecture. The honest disposition is RE-CLASSIFY as EQUIVALENT-IN-CURRENT-ARCHITECTURE and document the architectural constraint blocking independent killability — NOT ship a disjunction-based test that passes either way under the mutation (which is itself slop by the mutation-testing rubric's own discipline). Common trigger: sequential guards where guard N+1 can only fire when guard N also fires; mutating guard N+1's threshold is structurally unreachable so the surviving mutant is equivalent not gap. Sibling discipline to ai-slop-sentinel's "non-falsifying test" taxonomy: a test that passes under both current code AND the proposed mutation is exactly the slop pattern the mutation-testing rubric exists to surface — so writing one to "kill" the mutant defeats the entire purpose.
MrBinnacle/skills · ★ 0 · AI & Automation · score 68

Install: claude install-skill MrBinnacle/skills

# Mutation Equivalent-In-Current-Architecture ## Problem Mutation testing surfaces surviving mutants. The default disposition is to write a killing test (close the gap). But some surviving mutants are **structurally unreachable** by any falsifiable test in the current code architecture — usually because they're on a guard or branch that's never the FIRST guard/branch to fire on the relevant input domain. Naive response: write a test using a disjunction (`assert reason in ("A", "B")`) that "passes" against both current code and the mutation. This is double-slop: 1. The mutation isn't killed (the test passes under the mutation). 2. The test itself is the canonical ai-slop "tautological assertion / disjunction that passes either way" pattern that mutation testing exists to surface. Honest response: declare the mutant **EQUIVALENT-IN-CURRENT-ARCHITECTURE**, document the architectural constraint that blocks independent killability, and defer the architectural refactor (if desired) to a v-next punch list. The mutant remains uncovered in the report but the disposition is honest about why. ## Context / Trigger Conditions - A mutation-testing tool reports a surviving mutant. - Initial reading of the mutant suggests it's a genuine coverage gap. - On closer inspection, the mutated code path can only be reached via inputs that ALSO trigger an earlier guard which short-circuits before reaching the mutated line. - The earlier guard ALSO has a mutation on it (or a separate tes