fix(exchange): limit connection test to postgres access

tests/apps/exchange/test_service_units.py

@@ -173,8 +173,16 @@ class ExchangeConnectionServiceUnitTest(TestCase):
     def test_test_connection_payload_does_not_persist_connection(self):
         with patch.object(
             ExchangeConnectionService,
-            "validate_saved_connection",
-        ) as validate_mock:
+            "test_connection",
+            return_value="target_alias",
+        ) as test_connection_mock, patch.object(
+            ExchangeConnectionService,
+            "_cleanup_alias",
+        ) as cleanup_mock, patch.object(
+            ExchangeConnectionService,
+            "_validate_schema_exists",
+            side_effect=AssertionError("test-only connection check must not validate schema"),
+        ):
             result = ExchangeConnectionService.test_connection_payload(
                 server="127.0.0.1",
                 port=5432,
@@ -187,10 +195,11 @@ class ExchangeConnectionServiceUnitTest(TestCase):
         self.assertEqual(result["status"], "success")
         self.assertEqual(
             result["message"],
-            "Подключение проверено. Соединение и структура БД валидны.",
+            "Подключение проверено. PostgreSQL доступен, логин и пароль верны.",
         )
         self.assertEqual(ExchangeConnection.objects.count(), 0)
-        validate_mock.assert_called_once()
+        test_connection_mock.assert_called_once()
+        cleanup_mock.assert_called_once_with("target_alias")
 
     def test_get_active_connection_raises_when_missing(self):
         with self.assertRaisesMessage(