fix(proxy): proxy env setup

docs/changelog.md

@@ -1,5 +1,9 @@
 <!-- vale Canonical.007-Headings-sentence-case = NO -->
 
+## [#213 Fix proxy setup]
+
+- Fix proxy setup for image-relation joined hook.
+
 ## [#222 Add PPA for .NET backport during image building](https://github.com/canonical/github-runner-image-builder-operator/pull/222) (2026-05-22)
 
 - Add .NET PPA in image building. This allows wider range of .NET version to be installed.

tests/unit/test_image.py

@@ -99,7 +99,11 @@ def test__on_image_relation_joined(
     act: when _on_image_relation_joined hook is fired.
     assert: update_relation_data is called.
     """
-    monkeypatch.setattr(state.BuilderConfig, "from_charm", MagicMock())
+    mock_build_config = MagicMock()
+    mock_build_config.proxy = None
+    monkeypatch.setattr(
+        state.BuilderConfig, "from_charm", MagicMock(return_value=mock_build_config)
+    )
     monkeypatch.setattr(state.CloudsAuthConfig, "from_unit_relation_data", MagicMock())
     monkeypatch.setattr(builder, "install_clouds_yaml", MagicMock())
     monkeypatch.setattr(builder, "get_latest_images", MagicMock(return_value="test-id"))