diff --git a/tests/unit/test_unified_render_service.py b/tests/unit/test_unified_render_service.py
index 23244cc54..f2bba9f49 100755
--- a/tests/unit/test_unified_render_service.py
+++ b/tests/unit/test_unified_render_service.py
@@ -1928,7 +1928,6 @@ class TestConcatNormalizeVideoResolution:
         vf_value = cmd[vf_idx + 1]
         assert "crop=" in vf_value, "background 层应有 crop 滤镜"
 
-
     def test_pass_through_speed_up_correct_duration(self):
         """直通模式加速（speed=2x）：视频+音频均调速，-t 时长为原始的 1/2。"""
         clips = [_make_clip("c1", "main", order=0, duration=10.0, playback_speed=2.0)]