Harden external file connector boundaries

tests/test_storage_backends.py

@@ -0,0 +1,64 @@
+from __future__ import annotations
+
+import io
+import unittest
+from unittest.mock import MagicMock, PropertyMock, patch
+
+from govoplan_files.backend.storage.backends import S3StorageBackend, StorageBackendError
+
+
+def _backend() -> S3StorageBackend:
+    return S3StorageBackend(
+        bucket="files",
+        endpoint_url="https://objects.example.test",
+        region_name="test",
+        access_key_id="access",
+        secret_access_key="secret",
+    )
+
+
+class S3StorageBackendTests(unittest.TestCase):
+    def test_get_bytes_rejects_declared_oversize_object_without_reading(self) -> None:
+        body = MagicMock()
+        client = MagicMock()
+        client.get_object.return_value = {"ContentLength": 6, "Body": body}
+        with patch.dict("os.environ", {"GOVOPLAN_CONNECTOR_MAX_FILE_TRANSFER_BYTES": "5"}), patch.object(
+            S3StorageBackend,
+            "client",
+            new_callable=PropertyMock,
+            return_value=client,
+        ), self.assertRaisesRegex(StorageBackendError, "deployment limit"):
+            _backend().get_bytes("large.bin")
+        body.read.assert_not_called()
+        body.close.assert_called_once_with()
+
+    def test_iter_bytes_rejects_undeclared_oversize_object(self) -> None:
+        client = MagicMock()
+        client.get_object.return_value = {"Body": io.BytesIO(b"123456")}
+        with patch.dict("os.environ", {"GOVOPLAN_CONNECTOR_MAX_FILE_TRANSFER_BYTES": "5"}), patch.object(
+            S3StorageBackend,
+            "client",
+            new_callable=PropertyMock,
+            return_value=client,
+        ), self.assertRaisesRegex(StorageBackendError, "deployment limit"):
+            list(_backend().iter_bytes("large.bin", chunk_size=3))
+
+    def test_iter_bytes_closes_streaming_body_when_consumer_stops_early(self) -> None:
+        body = MagicMock()
+        body.read.side_effect = (b"123", b"456", b"")
+        client = MagicMock()
+        client.get_object.return_value = {"ContentLength": 6, "Body": body}
+        with patch.dict("os.environ", {"GOVOPLAN_CONNECTOR_MAX_FILE_TRANSFER_BYTES": "10"}), patch.object(
+            S3StorageBackend,
+            "client",
+            new_callable=PropertyMock,
+            return_value=client,
+        ):
+            chunks = _backend().iter_bytes("object.bin", chunk_size=3)
+            self.assertEqual(b"123", next(chunks))
+            chunks.close()
+        body.close.assert_called_once_with()
+
+
+if __name__ == "__main__":
+    unittest.main()