diff --git a/tests/unit/test_subtitle_render_engine.py b/tests/unit/test_subtitle_render_engine.py
index 66efa4fdc..5f8dd3da0 100755
--- a/tests/unit/test_subtitle_render_engine.py
+++ b/tests/unit/test_subtitle_render_engine.py
@@ -244,6 +244,16 @@ class TestWrapText:
         result = _wrap_text(text, 1)
         assert result == ["a", "b", "c"]
 
+    def test_max_chars_zero(self):
+        # 边界情况
+        text = "abc"
+        result = _wrap_text(text, 0)
+        # 0的话，max_chars//2也是0，range不会执行
+        # 按逻辑 len(text) > 0 成立，但 break_point 从 0 开始
+        # 这取决于具体实现，只要不崩溃就行
+        assert isinstance(result, list)
+        assert len(result) > 0
+
     def test_punctuation_at_boundary(self):
         # 标点刚好在 max_chars 位置
         text = "一二三四五六七八九。"