test: wire pytest test harness with standard hass fixture

tests/conftest.py

@@ -0,0 +1,58 @@
+"""Shared pytest fixtures for the NestQuest test suite.
+
+pytest-homeassistant-custom-component could not be adopted: it pins
+``pytest==9.0.3`` and ``voluptuous==0.13.1``, which conflicts with the dev
+group's ``voluptuous>=0.14`` (used directly by the options flow's schema and
+its tests), and its back-releases raise the floor to Python >=3.12 while this
+project supports >=3.11.  The documented fallback is therefore used:
+``pytest-asyncio`` plus a standard-shaped ``hass`` fixture below.
+
+The tests mock the ``homeassistant`` package via ``sys.modules`` injection;
+this conftest wires the mock modules before any test module import and
+provides the standard ``hass`` fixture shape (``config``, ``config_entries``,
+``data``, ``loop``) that HA's own harness exposes.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import sys
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+
+# Mock homeassistant modules if not installed in the environment.  Runs in
+# conftest so it precedes every test module's import of the integration.
+for _mod in (
+    "homeassistant",
+    "homeassistant.core",
+    "homeassistant.config_entries",
+    "homeassistant.data_entry_flow",
+):
+    sys.modules.setdefault(_mod, MagicMock())
+
+# Wire parent package attributes so "from homeassistant import config_entries"
+# resolves to the mocked submodule, mirroring real HA's package layout.
+sys.modules["homeassistant"].config_entries = sys.modules["homeassistant.config_entries"]
+sys.modules["homeassistant"].data_entry_flow = sys.modules["homeassistant.data_entry_flow"]
+
+
+@pytest.fixture
+def hass():
+    """Provide a standard-shaped hass fixture.
+
+    Mirrors the surface of Home Assistant's ``hass`` fixture: a ``config``
+    namespace, a ``config_entries`` manager, a ``data`` dict for integration
+    state, and the running event ``loop``.
+    """
+    hass = SimpleNamespace(
+        data={},
+        config=MagicMock(),
+        config_entries=MagicMock(),
+    )
+    hass.loop = asyncio.new_event_loop()
+    try:
+        yield hass
+    finally:
+        hass.loop.close()