diff --git a/doco/tests/test_video_split.py b/doco/tests/test_video_split.py
index 944e166..30b6934 100644
--- a/doco/tests/test_video_split.py
+++ b/doco/tests/test_video_split.py
@@ -163,7 +163,7 @@ class TestIsBlankFrame:
         img_path = tmp_path / "subtitle.png"
         arr = np.zeros((100, 100), dtype=np.uint8)
         # 1% 白像素(亮度255),其余黑(亮度0)
-        arr[:100, :10] = 255
+        arr[:10, :10] = 255  # 10×10=100/10000=1%
         img = Image.fromarray(arr, mode="L")
         img.save(img_path)
 
@@ -189,17 +189,18 @@ class TestIsBlankFrame:
         assert white_ratio < 0.005
 
     def test_ratio_ok_but_max_brightness_too_low(self, tmp_path):
-        """white_ratio>=0.005 但 max_brightness<240 → is_blank=True"""
+        """max_brightness<240 → 白像素计数全为0 → is_blank=True"""
         from PIL import Image
         import numpy as np
         img_path = tmp_path / "dim_pixels.png"
         arr = np.zeros((100, 100), dtype=np.uint8)
-        # 1% 像素亮度=220(不够240阈值),其余黑
-        arr[:100, :10] = 220
+        # 1% 像素亮度=220(不满足阈值240),其余黑
+        # is_blank_frame 用 arr > 240 统计白像素,220 全不满足 → white_ratio=0
+        arr[:10, :10] = 220
         img = Image.fromarray(arr, mode="L")
         img.save(img_path)
 
         is_blank, white_ratio, max_brightness = is_blank_frame(img_path)
         assert is_blank is True
         assert max_brightness == 220
-        assert white_ratio >= 0.005
+        assert white_ratio == 0.0