diff --git a/tests/unit/test_generation_preview.py b/tests/unit/test_generation_preview.py
index d3fcd497f..139faa03e 100755
--- a/tests/unit/test_generation_preview.py
+++ b/tests/unit/test_generation_preview.py
@@ -726,7 +726,7 @@ class TestCreatePreviewRoute:
                     self._make_request(),
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                 )
         assert resp.task_id == "preview_task_001"
         assert resp.status == "pending"
@@ -780,7 +780,7 @@ class TestCreatePreviewRoute:
                     self._make_request(),
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                 )
             assert exc_info.value.status_code == 400
 
@@ -799,7 +799,7 @@ class TestCreatePreviewRoute:
                     self._make_request(),
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                 )
             assert exc_info.value.status_code == 500
 
@@ -823,7 +823,7 @@ class TestCreatePreviewRoute:
                         self._make_request(),
                         authenticated_user=_make_user(),
                         generation_task_repository=repo,
-                db=MagicMock(),
+                        db=MagicMock(),
                     )
                 assert exc_info.value.status_code == 500
 
@@ -847,7 +847,7 @@ class TestCreatePreviewRoute:
                         self._make_request(),
                         authenticated_user=_make_user(),
                         generation_task_repository=repo,
-                db=MagicMock(),
+                        db=MagicMock(),
                     )
                 assert exc_info.value.status_code == 429
 
@@ -871,7 +871,7 @@ class TestCreatePreviewRoute:
                         self._make_request(),
                         authenticated_user=_make_user(),
                         generation_task_repository=repo,
-                db=MagicMock(),
+                        db=MagicMock(),
                     )
                 assert exc_info.value.status_code == 503
 
@@ -893,7 +893,7 @@ class TestGetPreviewRoute:
                     task_id="nonexistent",
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                     generated_video_repository=vid_repo,
                 )
             assert exc_info.value.status_code == 404
@@ -914,7 +914,7 @@ class TestGetPreviewRoute:
                     task_id="preview_task_001",
                     authenticated_user=_make_user("test_user_001"),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                     generated_video_repository=vid_repo,
                 )
             assert exc_info.value.status_code == 403
@@ -935,7 +935,7 @@ class TestGetPreviewRoute:
                     task_id="preview_task_001",
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                     generated_video_repository=vid_repo,
                 )
             assert exc_info.value.status_code == 404
@@ -974,7 +974,7 @@ class TestGetPreviewRoute:
                     task_id="preview_task_001",
                     authenticated_user=_make_user(),
                     generation_task_repository=repo,
-                db=MagicMock(),
+                    db=MagicMock(),
                     generated_video_repository=vid_repo,
                 )
             assert exc_info.value.status_code == 403
@@ -1003,7 +1003,7 @@ class TestGetPreviewRoute:
                         task_id="preview_task_001",
                         authenticated_user=_make_user(),
                         generation_task_repository=repo,
-                db=MagicMock(),
+                        db=MagicMock(),
                         generated_video_repository=vid_repo,
                     )
         assert resp.video_url == "https://cdn.example.com/preview_final.mp4?sig=abc123"
@@ -1168,7 +1168,6 @@ class TestCalcPreviewResolution:
         assert _calc_preview_resolution("") == "854x480"
 
 
-
 class TestInferVideoRatioFromTemplate:
     """_infer_video_ratio_from_template 单元测试。"""
 
@@ -1180,9 +1179,7 @@ class TestInferVideoRatioFromTemplate:
         mock_template.mode = "pip"
         mock_db = MagicMock()
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.return_value.get_by_id.return_value = mock_template
             result = _infer_video_ratio_from_template("tpl_001", mock_db)
         assert result == "9:16"
@@ -1195,9 +1192,7 @@ class TestInferVideoRatioFromTemplate:
         mock_template.mode = "standard"
         mock_db = MagicMock()
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.return_value.get_by_id.return_value = mock_template
             result = _infer_video_ratio_from_template("tpl_001", mock_db)
         assert result == "16:9"
@@ -1210,9 +1205,7 @@ class TestInferVideoRatioFromTemplate:
         mock_template.mode = "unknown_mode"
         mock_db = MagicMock()
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.return_value.get_by_id.return_value = mock_template
             result = _infer_video_ratio_from_template("tpl_001", mock_db)
         assert result == ""
@@ -1223,9 +1216,7 @@ class TestInferVideoRatioFromTemplate:
 
         mock_db = MagicMock()
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.return_value.get_by_id.return_value = None
             result = _infer_video_ratio_from_template("nonexistent", mock_db)
         assert result == ""
@@ -1244,9 +1235,7 @@ class TestInferVideoRatioFromTemplate:
 
         mock_db = MagicMock()
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.side_effect = Exception("db connection error")
             result = _infer_video_ratio_from_template("tpl_001", mock_db)
         assert result == ""
@@ -1293,13 +1282,9 @@ class TestPreviewRouteAutoInfersVideoRatio:
             bgm_config={},
         )
 
-        with patch(
-            "app.api.routes.generation_preview.SQLAlchemyTemplateRepository"
-        ) as MockRepo:
+        with patch("app.api.routes.generation_preview.SQLAlchemyTemplateRepository") as MockRepo:
             MockRepo.return_value.get_by_id.return_value = mock_template
-            with patch(
-                "app.api.routes.generation_preview.CreateGenerationTaskUseCase"
-            ) as MockUC:
+            with patch("app.api.routes.generation_preview.CreateGenerationTaskUseCase") as MockUC:
                 MockUC.return_value.execute.return_value = task
                 with patch(
                     "app.api.routes.generation_preview.safe_enqueue_generation_task",