Add missing test case that also covers steam boilers

Signed-off-by: Simon Völcker <simon.voelcker@frequenz.com>

Author: simonvoelcker

tests/client_test_cases/list_microgrid_electrical_components/success_case.py

@@ -0,0 +1,49 @@
+# License: MIT
+# Copyright © 2026 Frequenz Energy-as-a-Service GmbH
+
+"""Test data for successful electrical component listing."""
+
+from typing import Any
+
+from frequenz.api.assets.v1 import assets_pb2
+from frequenz.api.common.v1alpha8.microgrid.electrical_components import (
+    electrical_components_pb2,
+)
+from frequenz.client.common.microgrid import MicrogridId
+from frequenz.client.common.microgrid.electrical_components import ElectricalComponentId
+
+from frequenz.client.assets.electrical_component import SteamBoiler
+
+
+def assert_stub_method_call(stub_method: Any) -> None:
+    """Assert that the gRPC request matches the expected request."""
+    stub_method.assert_called_once_with(
+        assets_pb2.ListMicrogridElectricalComponentsRequest(microgrid_id=1234),
+        timeout=60.0,
+    )
+
+
+client_args = (1234,)
+grpc_response = assets_pb2.ListMicrogridElectricalComponentsResponse(
+    components=[
+        electrical_components_pb2.ElectricalComponent(
+            id=1,
+            microgrid_id=1234,
+            category=electrical_components_pb2.ELECTRICAL_COMPONENT_CATEGORY_STEAM_BOILER,
+            name="Steam Boiler",
+        )
+    ]
+)
+
+
+def assert_client_result(result: Any) -> None:
+    """Assert that the client result matches the expected component list."""
+    assert list(result) == [
+        SteamBoiler(
+            id=ElectricalComponentId(1),
+            microgrid_id=MicrogridId(1234),
+            name="Steam Boiler",
+            manufacturer=None,
+            model_name=None,
+        )
+    ]