Couple more tests

Author: wesm

moneyflow/ynab_client.py

@@ -580,6 +580,24 @@ def _batch_reassign_transactions(
         Returns:
             Dictionary with results (same format as batch_update_merchant)
         """
+        # Guard against attempting to reassign payee to itself
+        if old_payee_id == target_payee_id:
+            logger.warning(
+                f"Attempted to reassign payee {old_payee_id} to itself. "
+                f"This suggests '{old_merchant_name}' and '{new_merchant_name}' "
+                "are the same payee (possible duplicate)."
+            )
+            return {
+                "success": False,
+                "payee_id": old_payee_id,
+                "transactions_affected": 0,
+                "method": "same_payee_error",
+                "message": (
+                    f"Cannot reassign: '{old_merchant_name}' and '{new_merchant_name}' "
+                    f"are the same payee (id={old_payee_id})"
+                ),
+            }
+
         try:
             transactions_api = ynab.TransactionsApi(self.api_client)
 

tests/test_ynab_backend.py

@@ -547,6 +547,40 @@ def test_batch_update_merchant_target_exists(self, backend, mock_ynab_api):
         )
         mock_transactions_api.update_transactions.assert_called_once()
 
+    def test_batch_update_merchant_same_payee_id(self, backend, mock_ynab_api):
+        """Test that reassigning to the same payee ID is rejected."""
+        backend.client.budget_id = "test-budget-id"
+        backend.client.api_client = MagicMock()
+
+        # Mock two payees with different names but same ID (edge case - shouldn't happen but guard against it)
+        mock_old_payee = MagicMock()
+        mock_old_payee.id = "payee-same"
+        mock_old_payee.name = "Amazon.com"
+
+        mock_target_payee = MagicMock()
+        mock_target_payee.id = "payee-same"  # Same ID!
+        mock_target_payee.name = "Amazon"
+
+        mock_payees_response = MagicMock()
+        mock_payees_response.data.payees = [mock_old_payee, mock_target_payee]
+
+        mock_payees_api = MagicMock()
+        mock_payees_api.get_payees.return_value = mock_payees_response
+
+        mock_ynab_api.PayeesApi.return_value = mock_payees_api
+
+        # Attempt to rename payee to itself (simulating a bug where names differ but ID is same)
+        result = backend.batch_update_merchant("Amazon.com", "Amazon")
+
+        # Should fail with same_payee_error
+        assert result["success"] is False
+        assert result["method"] == "same_payee_error"
+        assert "same payee" in result["message"]
+        assert result["payee_id"] == "payee-same"
+
+        # Verify no API calls were made to update transactions
+        mock_payees_api.update_payee.assert_not_called()
+
     def test_batch_update_merchant_integration(self, backend, mock_ynab_api):
         """
         Integration test: Verify that batch_update_merchant cascades to transactions.