Allow exposing entities not in the entity registry to assistants (#92363)

tests/components/demo/conftest.py

@@ -1,3 +1,14 @@
 """demo conftest."""
+import pytest
+
+from homeassistant.core import HomeAssistant
+from homeassistant.setup import async_setup_component
+
 from tests.components.blueprint.conftest import stub_blueprint_populate  # noqa: F401
 from tests.components.light.conftest import mock_light_profiles  # noqa: F401
+
+
+@pytest.fixture(autouse=True)
+async def setup_homeassistant(hass: HomeAssistant):
+    """Set up the homeassistant integration."""
+    await async_setup_component(hass, "homeassistant", {})