test: 修复 EPUB 缺失依赖测试设计问题

tests/test_splitters_epub.py

@@ -1,11 +1,30 @@
 """EPUBSplitter 测试."""
 import pytest
 
-ebooklib = pytest.importorskip("ebooklib", reason="ebooklib 未安装")
+
+class TestEPUBSplitterMissingDep:
+    """缺失依赖时的行为测试（不 skip 整个文件）."""
+
+    def test_split_raises_clear_import_error(self, monkeypatch):
+        """未安装 ebooklib 时给出明确提示."""
+        from src.core.splitters.epub import EPUBSplitter
+        s = EPUBSplitter()
+        import builtins
+        original_import = builtins.__import__
+
+        def mock_import(name, *args, **kwargs):
+            if name == "ebooklib" or name.startswith("ebooklib."):
+                raise ImportError("No module named 'ebooklib'")
+            return original_import(name, *args, **kwargs)
+
+        monkeypatch.setattr(builtins, "__import__", mock_import)
+        with pytest.raises(ImportError, match="ebooklib"):
+            s.split("dummy.epub", source_file="test.epub")
 
 
 class TestEPUBSplitter:
     """EPUBSplitter 测试（需 ebooklib）."""
+    ebooklib = pytest.importorskip("ebooklib", reason="ebooklib 未安装")
 
     def test_split_simple_epub(self, tmp_path):
         """用 ebooklib 创建一个简单 EPUB 并测试分块."""
@@ -47,10 +66,3 @@ class TestEPUBSplitter:
         from src.core.splitters.epub import EPUBSplitter
         s = EPUBSplitter()
         assert hasattr(s, "split")
-
-    def test_epub_missing_dependency_message(self):
-        """EPUBSplitter.split() 在未安装 ebooklib 时应给出明确提示."""
-        from src.core.splitters.epub import EPUBSplitter
-        s = EPUBSplitter()
-        # 验证 split 方法存在且可调用（有明确的 import error 信息）
-        assert callable(s.split)