diff --git a/tests/unit/test_wechat_sync_use_case.py b/tests/unit/test_wechat_sync_use_case.py
index 9776faf9b..eb12e4598 100755
--- a/tests/unit/test_wechat_sync_use_case.py
+++ b/tests/unit/test_wechat_sync_use_case.py
@@ -325,9 +325,7 @@ class TestWechatSyncSession:
 class TestWechatSyncNicknameRules:
     """昵称规则：默认昵称、登录不覆盖存量昵称、中文昵称全链路无损。"""
 
-    def test_existing_user_display_name_never_overwritten_on_login(
-        self, mock_user_repo, mock_session_store
-    ):
+    def test_existing_user_display_name_never_overwritten_on_login(self, mock_user_repo, mock_session_store):
         """守护规则：已存在用户登录时，即使请求带了别的 nickname，
         其 display_name 也绝不能被覆盖（只有建号时写入）。"""
         user = User(
@@ -360,9 +358,7 @@ class TestWechatSyncNicknameRules:
         for call in mock_user_repo.save.call_args_list:
             assert call.args[0].display_name == "我的专属昵称"
 
-    def test_new_user_gets_default_nickname_when_nickname_empty(
-        self, mock_user_repo, mock_session_store
-    ):
+    def test_new_user_gets_default_nickname_when_nickname_empty(self, mock_user_repo, mock_session_store):
         """新用户且请求未带昵称（微信新规场景）→ 默认昵称小虾同学。"""
         saved = {}
         mock_user_repo.save.side_effect = lambda u: saved.update({u.id: u})
@@ -375,9 +371,7 @@ class TestWechatSyncNicknameRules:
         assert u.display_name == "小虾同学"
         assert resp.nickname == "小虾同学"
 
-    def test_chinese_nickname_full_chain_no_mojibake(
-        self, mock_user_repo, mock_session_store
-    ):
+    def test_chinese_nickname_full_chain_no_mojibake(self, mock_user_repo, mock_session_store):
         """中文昵称全链路无损：建号写入 → 仓储对象 → 响应返回，
         不允许出现 latin-1/utf-8 双重编码乱码（如 \u00e8\u0080\u0081 一类）。"""
         chinese_name = "老字号🏮肩腰腿🏮御众堂永康店"