fix: EnvHelper unusable if error occurs during initialisation (#954)

code/backend/batch/utilities/helpers/env_helper.py

@@ -15,8 +15,9 @@ class EnvHelper:
     def __new__(cls):
         with cls._lock:
             if cls._instance is None:
-                cls._instance = super(EnvHelper, cls).__new__(cls)
-                cls._instance.__load_config()
+                instance = super(EnvHelper, cls).__new__(cls)
+                instance.__load_config()
+                cls._instance = instance
             return cls._instance
 
     def __load_config(self, **kwargs) -> None:

code/tests/utilities/helpers/test_env_helper.py

@@ -1,3 +1,4 @@
+from unittest.mock import patch
 from pytest import MonkeyPatch
 import pytest
 from backend.batch.utilities.helpers.env_helper import EnvHelper
@@ -140,3 +141,16 @@ def test_use_advanced_image_processing(monkeypatch: MonkeyPatch, value, expected
 
     # then
     assert actual_use_advanced_image_processing == expected
+
+
+@patch(
+    "backend.batch.utilities.helpers.env_helper.os.getenv",
+    side_effect=Exception("Some error"),
+)
+def test_env_helper_not_created_if_error_occurs(_):
+    # when
+    with pytest.raises(Exception):
+        EnvHelper()
+
+    # then
+    assert EnvHelper._instance is None