diff --git a/tests/unit/test_preview_generation_fixes.py b/tests/unit/test_preview_generation_fixes.py
index 23781db72..9705a8edf 100644
--- a/tests/unit/test_preview_generation_fixes.py
+++ b/tests/unit/test_preview_generation_fixes.py
@@ -7,7 +7,6 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
-
 # ── Fix 1: URL 签名 ──────────────────────────────────────────────────────────
 
 
@@ -78,8 +77,8 @@ class TestLoadTemplateSegmentDurations:
 
     def test_empty_template_id_returns_empty(self):
         """空 template_id 返回空列表。"""
-        import sys
         import os
+        import sys
 
         sys.path.insert(0, os.path.join(os.path.dirname(__file__), "apps", "worker"))
         from worker_app.tasks.generation import _load_template_segment_durations
@@ -155,11 +154,11 @@ class TestDurationCappingInBuildPlan:
 
     def test_clips_capped_by_segment_max(self):
         """clip 时长超过 segment duration_max 时应被截断。"""
-        from worker_app.tasks.generation import _build_plan_and_clips_from_task
-
         # 创建临时假视频文件
         import tempfile
 
+        from worker_app.tasks.generation import _build_plan_and_clips_from_task
+
         with tempfile.TemporaryDirectory() as tmpdir:
             paths = []
             for i in range(3):
@@ -193,10 +192,10 @@ class TestDurationCappingInBuildPlan:
 
     def test_clips_not_capped_when_under_max(self):
         """clip 时长小于 segment duration_max 时不截断。"""
-        from worker_app.tasks.generation import _build_plan_and_clips_from_task
-
         import tempfile
 
+        from worker_app.tasks.generation import _build_plan_and_clips_from_task
+
         with tempfile.TemporaryDirectory() as tmpdir:
             paths = [Path(tmpdir) / "video_0.mp4"]
             paths[0].write_bytes(b"\x00" * 100)
@@ -222,10 +221,10 @@ class TestDurationCappingInBuildPlan:
 
     def test_no_capping_without_template(self):
         """无 template_id 时不截断。"""
-        from worker_app.tasks.generation import _build_plan_and_clips_from_task
-
         import tempfile
 
+        from worker_app.tasks.generation import _build_plan_and_clips_from_task
+
         with tempfile.TemporaryDirectory() as tmpdir:
             paths = [Path(tmpdir) / "video_0.mp4"]
             paths[0].write_bytes(b"\x00" * 100)
@@ -250,14 +249,14 @@ class TestPreviewResolution:
 
     def test_preview_uses_passed_resolution(self):
         """is_preview=True 且有 resolution 参数时，使用传入的分辨率。"""
+        import tempfile
+
         from worker_app.tasks.generation import _render_video
 
         # 验证逻辑：检查 _render_video 在 is_preview + resolution 时的行为
         # 由于 _render_video 内部会调用 RenderAdapter，这里只验证分辨率配置逻辑
         # 通过 mock 掉渲染部分，检查 export_cfg
 
-        import tempfile
-
         with tempfile.TemporaryDirectory() as tmpdir:
             temp_path = Path(tmpdir)
             video_path = temp_path / "input.mp4"
@@ -322,10 +321,10 @@ class TestPreviewResolution:
 
     def test_preview_defaults_to_landscape_when_no_resolution(self):
         """is_preview=True 且无 resolution 参数时，默认 854x480。"""
-        from worker_app.tasks.generation import _render_video
-
         import tempfile
 
+        from worker_app.tasks.generation import _render_video
+
         with tempfile.TemporaryDirectory() as tmpdir:
             temp_path = Path(tmpdir)
             video_path = temp_path / "input.mp4"