Added test for testing fetch out-of-band utility

Author: jimmysway

process_report/tests/unit/invoices/test_base_invoice.py

@@ -1,5 +1,9 @@
 from unittest import TestCase, mock
 import pandas
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from unittest.mock import MagicMock
 
 from process_report.tests import util as test_utils
 
@@ -17,6 +21,33 @@ def test_filter_exported_columns(self):
 
         self.assertTrue(result_invoice.equals(answer_invoice))
 
+    @mock.patch("pandas.read_csv")
+    def test_fetch_with_mock_s3_bucket(self, mock_read_csv: "MagicMock") -> None:
+        """Test that fetch() method loads data correctly when S3 bucket is mocked."""
+        test_invoice = test_utils.new_base_invoice(
+            name="TestInvoice", invoice_month="2024-08"
+        )
+        expected_data = pandas.DataFrame(
+            {
+                "Invoice Month": ["2024-08", "2024-08"],
+                "Project - Allocation": ["P1", "P2"],
+                "Manager (PI)": ["[email protected]", "[email protected]"],
+                "Cost": [100.00, 150.00],
+            }
+        )
+        mock_read_csv.return_value = expected_data
+
+        mock_s3_bucket = mock.MagicMock()
+        mock_s3_bucket.download_file.return_value = None
+
+        test_invoice.fetch(mock_s3_bucket)
+
+        self.assertIsNotNone(test_invoice.data)
+        self.assertTrue(test_invoice.data.equals(expected_data))
+        mock_s3_bucket.download_file.assert_called_once_with(
+            "Invoices/2024-08/TestInvoice 2024-08.csv", "TestInvoice 2024-08.csv"
+        )
+
 
 class TestUploadToS3(TestCase):
     @mock.patch("process_report.util.get_invoice_bucket")