test(writer/qa): 覆盖 engine=None 委托工厂的真实门禁路径

tests/test_phase5_qa_loop.py

@@ -54,3 +54,14 @@ def test_qa_loop_regenerates_only_failed(tmp_path):
     assert report.passed is True
     assert engine.calls["A"] == 1   # A 首次即通过，未被重生成
     assert engine.calls["B"] == 2   # B 失败后被重生成一次
+
+
+def test_run_delegates_to_factory_when_engine_none(monkeypatch, tmp_path):
+    # 门禁真实路径：engine=None 时应委托 build_inference_engine() 构造真实引擎
+    monkeypatch.setattr("genesis.qa.qa_loop.build_inference_engine", lambda: ImprovingEngine())
+    tpl = tmp_path / "tpl.docx"
+    out = tmp_path / "out.docx"
+    _make_template(str(tpl))
+    loop = QALoop(max_rounds=3)
+    report = loop.run(_ss(str(tpl)), str(out), samples_dir="nonexistent_dir_xyz", engine=None)
+    assert report.passed is True