tests/test_adr_0250_q_difference_failclosed.py

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+"""ADR-0250 increment 1 — Q3 hazard-close: q:difference is fail-closed.
+
+Josh's Q3 ruling deferred the q:difference *capability* (its cases strand on
+multi-compound) but required the hazard be CLOSED now: the partial Pattern-B
+"how many more/fewer" path must never emit a guessed-direction answer. The
+direction bit ("more…than" → A−B vs "fewer…than" → B−A) is a wrong=0 driver
+that must be positively determined; until it is, the question MUST refuse.
+
+`_pattern_b_comparative_candidates` is inert by construction (returns []), so
+these questions refuse end-to-end. This suite LOCKS that so a future D.5 wiring
+cannot silently reopen the hazard without the direction determination. The
+critical cases are the ones where every STATEMENT injects cleanly — a guessed
+answer would be most likely there, and matching gold by luck would be a
+sealed-test wrong wearing a success costume.
+"""
+from __future__ import annotations
+
+import pytest
+
+from generate.math_candidate_graph import parse_and_solve
+
+# Each: statements parse cleanly; only the q:difference question is in play.
+# Every one MUST refuse (answer is None) — never a signed-difference answer.
+_Q_DIFFERENCE_PROBLEMS = [
+    "Alice has 10 apples. Bob has 4 apples. How many more apples does Alice have than Bob?",
+    "Alice has 10 apples. Bob has 4 apples. How many fewer apples does Bob have than Alice?",
+    "Whitney bought 9 books and 7 magazines. How many more books than magazines did Whitney buy?",
+    "Tom made 12 cookies. Sam made 5 cookies. How many more cookies did Tom make than Sam?",
+    "Mary has a bag holding 20 pounds. She buys 4 pounds of beans. How many more pounds can Mary fit?",
+]
+
+
+@pytest.mark.parametrize("problem", _Q_DIFFERENCE_PROBLEMS)
+def test_q_difference_refuses_no_guessed_direction(problem: str) -> None:
+    result = parse_and_solve(problem)
+    assert result.answer is None, (
+        "q:difference must refuse (deferred capability, hazard closed): a "
+        f"guessed-direction answer {result.answer!r} is a wrong=0 hole. Problem: {problem!r}"
+    )