[API] Sub devices and areas (#8544)

Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick+github@koston.org>

tests/unit_tests/core/conftest.py

@@ -0,0 +1,18 @@
+"""Shared fixtures for core unit tests."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def yaml_file(tmp_path: Path) -> Callable[[str], str]:
+    """Create a temporary YAML file for testing."""
+
+    def _yaml_file(content: str) -> str:
+        yaml_path = tmp_path / "test.yaml"
+        yaml_path.write_text(content)
+        return str(yaml_path)
+
+    return _yaml_file