fix(test): 修复 MagicMock 属性自动创建导致的断言失败

使用 FakeGenTask 替代 MagicMock，通过追踪 _assigned 字典
准确判断 cover_url 是否被显式设置。

tests/unit/test_cover_url_finalize.py

@@ -6,9 +6,32 @@ from cover_candidates to gen_task.cover_url.
 
 from __future__ import annotations
 
+import sys
 from pathlib import Path
 from unittest.mock import MagicMock, patch
 
+import pytest
+
+# Add worker app to sys.path
+_WORKER_ROOT = Path(__file__).resolve().parents[2] / "apps" / "worker"
+if str(_WORKER_ROOT) not in sys.path:
+    sys.path.insert(0, str(_WORKER_ROOT))
+
+
+class FakeGenTask:
+    """Simple stand-in for GenerationTask that tracks attribute assignment."""
+
+    def __init__(self):
+        self.id = "task-1"
+        self.status = MagicMock()
+        self.status.value = "running"
+        self._assigned = {}
+
+    def __setattr__(self, name, value):
+        if not name.startswith("_"):
+            self._assigned[name] = value
+        super().__setattr__(name, value)
+
 
 def _make_plan():
     plan = MagicMock()
@@ -19,19 +42,11 @@ def _make_plan():
     return plan
 
 
-def _make_gen_task():
-    gen_task = MagicMock()
-    gen_task.id = "task-1"
-    gen_task.status = MagicMock()
-    gen_task.status.value = "running"
-    return gen_task
-
-
 def _call_finalize(cover_candidates=None, gen_task=None, plan=None):
     from worker_app.tasks.edit_plan_generation import _finalize_render_success
 
     plan = plan or _make_plan()
-    gen_task = gen_task or _make_gen_task()
+    gen_task = gen_task or FakeGenTask()
 
     plan_repo = MagicMock()
     clip_repo = MagicMock()
@@ -86,25 +101,26 @@ class TestFinalizeCoverUrl:
     def test_cover_url_not_set_when_empty_list(self):
         """Empty cover_candidates should not set cover_url"""
         _, gen_task, _ = _call_finalize(cover_candidates=[])
-        assert not getattr(gen_task, "cover_url", None)
+        assert "cover_url" not in gen_task._assigned
 
     def test_cover_url_not_set_when_none(self):
         """None cover_candidates should not set cover_url"""
         _, gen_task, _ = _call_finalize(cover_candidates=None)
-        assert not getattr(gen_task, "cover_url", None)
+        assert "cover_url" not in gen_task._assigned
 
     def test_cover_url_not_set_when_url_empty(self):
         """Empty URL strings in candidates should not set cover_url"""
         candidates = [{"image_url": "", "url": ""}]
         _, gen_task, _ = _call_finalize(cover_candidates=candidates)
-        assert not getattr(gen_task, "cover_url", None)
+        assert "cover_url" not in gen_task._assigned
 
     def test_no_generation_task_no_crash(self):
         """Should not crash when gen_task is None"""
         candidates = [{"image_url": "https://oss.example.com/cover.jpg"}]
         gen_task_repo = MagicMock()
         gen_task_repo.get.return_value = None
-        _, _, _ = _call_finalize(cover_candidates=candidates)
+        result, _, _ = _call_finalize(cover_candidates=candidates)
+        assert result["status"] == "completed"
 
     def test_image_url_priority_over_url(self):
         """image_url should take priority over url key"""