Stabilize desktop migration tests on Windows

backend/tests/unit/test_desktop_migration.py

@@ -45,9 +45,35 @@ def _stub_package(name):
     return mod
 
 
+def _remove_module_tree(prefix):
+    for name in list(sys.modules):
+        if name == prefix or name.startswith(prefix + "."):
+            sys.modules.pop(name, None)
+
+
+def _ensure_package_path(name, path):
+    mod = sys.modules.get(name)
+    if not isinstance(mod, types.ModuleType):
+        mod = types.ModuleType(name)
+        sys.modules[name] = mod
+    mod.__path__ = [str(path)]
+    return mod
+
+
 # ---------------------------------------------------------------------------
 # Stub heavy dependencies before any production imports
 # ---------------------------------------------------------------------------
+for module_prefix in [
+    "database",
+    "models",
+    "utils",
+    "routers.chat_sessions",
+    "routers.focus_sessions",
+    "routers.advice",
+    "routers.staged_tasks",
+]:
+    _remove_module_tree(module_prefix)
+
 for mod_name in [
     "firebase_admin",
     "firebase_admin.firestore",
@@ -83,17 +109,14 @@ def _stub_package(name):
 sys.modules["google.cloud.firestore_v1"].FieldFilter = field_filter_stub.FieldFilter
 sys.modules["google.cloud.firestore_v1"].transactional = lambda f: f
 
+redis_stub = sys.modules["database.redis_db"]
+redis_stub.try_acquire_user_platform_write_lock = MagicMock(return_value=True)
+
 # Add backend dir to sys.path
 sys.path.insert(0, str(BACKEND_DIR))
 
 # Stub database package and _client
-if "database" not in sys.modules:
-    db_pkg = _stub_package("database")
-    db_pkg.__path__ = [str(BACKEND_DIR / "database")]
-else:
-    db_mod = sys.modules["database"]
-    if not hasattr(db_mod, '__path__'):
-        db_mod.__path__ = [str(BACKEND_DIR / "database")]
+_ensure_package_path("database", BACKEND_DIR / "database")
 
 client_stub = _stub_module("database._client")
 mock_db = MagicMock()
@@ -148,6 +171,10 @@ def _stub_package(name):
 from routers.advice import CreateAdviceRequest  # noqa: E402
 from routers.staged_tasks import BatchUpdateScoresRequest, BatchScoreEntry  # noqa: E402
 
+_ensure_package_path("models", BACKEND_DIR / "models")
+_ensure_package_path("utils", BACKEND_DIR / "utils")
+_ensure_package_path("utils.other", BACKEND_DIR / "utils" / "other")
+
 # Cannot import routers.users directly — it pulls in database.conversations → utils.other.hume
 # which has heavy deps. Mirror the models here and verify parity via AST test below.
 
@@ -1358,7 +1385,7 @@ def test_notification_settings_fields_match_source(self):
         """Inline UpdateNotificationSettingsRequest matches routers/users.py definition."""
         import ast
 
-        source = (BACKEND_DIR / 'routers' / 'users.py').read_text()
+        source = (BACKEND_DIR / 'routers' / 'users.py').read_text(encoding='utf-8')
         tree = ast.parse(source)
         for node in ast.walk(tree):
             if isinstance(node, ast.ClassDef) and node.name == 'UpdateNotificationSettingsRequest':
@@ -1377,7 +1404,7 @@ def test_llm_usage_fields_match_source(self):
         """Inline RecordLlmUsageBucketRequest matches routers/users.py definition."""
         import ast
 
-        source = (BACKEND_DIR / 'routers' / 'users.py').read_text()
+        source = (BACKEND_DIR / 'routers' / 'users.py').read_text(encoding='utf-8')
         tree = ast.parse(source)
         for node in ast.walk(tree):
             if isinstance(node, ast.ClassDef) and node.name == 'RecordLlmUsageBucketRequest':
@@ -1694,10 +1721,14 @@ def test_returns_title(self, mock_update):
             session_id='s1',
             messages=[TitleMessageInput(text='hi', sender='human'), TitleMessageInput(text='hello', sender='ai')],
         )
-        with patch.dict('sys.modules', {'utils.llm.clients': MagicMock(llm_mini=mock_llm)}):
+        mock_get_llm = MagicMock(return_value=mock_llm)
+        llm_clients_stub = types.ModuleType('utils.llm.clients')
+        llm_clients_stub.get_llm = mock_get_llm
+        with patch.dict('sys.modules', {'utils.llm.clients': llm_clients_stub}):
             result = generate_session_title(request, uid='u1')
 
         assert result == {'title': 'Project Discussion'}
+        mock_get_llm.assert_called_once_with('session_titles')
         mock_update.assert_called_once_with('u1', 's1', title='Project Discussion')
 
     @patch('database.chat.update_chat_session')
@@ -1713,10 +1744,14 @@ def test_empty_response_defaults_to_new_chat(self, mock_update):
             session_id='s1',
             messages=[TitleMessageInput(text='hi', sender='human')],
         )
-        with patch.dict('sys.modules', {'utils.llm.clients': MagicMock(llm_mini=mock_llm)}):
+        mock_get_llm = MagicMock(return_value=mock_llm)
+        llm_clients_stub = types.ModuleType('utils.llm.clients')
+        llm_clients_stub.get_llm = mock_get_llm
+        with patch.dict('sys.modules', {'utils.llm.clients': llm_clients_stub}):
             result = generate_session_title(request, uid='u1')
 
         assert result == {'title': 'New Chat'}
+        mock_get_llm.assert_called_once_with('session_titles')
 
 
 class TestChatMessageCount: