Restore state of trend sensor (#100332)

* Restoring state of trend sensor

* Handle unknown state & parametrize tests

homeassistant/components/trend/binary_sensor.py

@@ -25,6 +25,7 @@ from homeassistant.const import (
     CONF_ENTITY_ID,
     CONF_FRIENDLY_NAME,
     CONF_SENSORS,
+    STATE_ON,
     STATE_UNAVAILABLE,
     STATE_UNKNOWN,
 )
@@ -37,6 +38,7 @@ from homeassistant.helpers.event import (
     async_track_state_change_event,
 )
 from homeassistant.helpers.reload import async_setup_reload_service
+from homeassistant.helpers.restore_state import RestoreEntity
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType, EventType
 from homeassistant.util.dt import utcnow
 
@@ -116,7 +118,7 @@ async def async_setup_platform(
     async_add_entities(sensors)
 
 
-class SensorTrend(BinarySensorEntity):
+class SensorTrend(BinarySensorEntity, RestoreEntity):
     """Representation of a trend Sensor."""
 
     _attr_should_poll = False
@@ -194,6 +196,12 @@ class SensorTrend(BinarySensorEntity):
             )
         )
 
+        if not (state := await self.async_get_last_state()):
+            return
+        if state.state == STATE_UNKNOWN:
+            return
+        self._state = state.state == STATE_ON
+
     async def async_update(self) -> None:
         """Get the latest data and update the states."""
         # Remove outdated samples

tests/components/trend/test_binary_sensor.py

@@ -2,16 +2,19 @@
 from datetime import timedelta
 from unittest.mock import patch
 
+import pytest
+
 from homeassistant import config as hass_config, setup
 from homeassistant.components.trend.const import DOMAIN
 from homeassistant.const import SERVICE_RELOAD, STATE_UNKNOWN
-from homeassistant.core import HomeAssistant
+from homeassistant.core import HomeAssistant, State
 import homeassistant.util.dt as dt_util
 
 from tests.common import (
     assert_setup_component,
     get_fixture_path,
     get_test_home_assistant,
+    mock_restore_cache,
 )
 
 
@@ -413,3 +416,28 @@ async def test_reload(hass: HomeAssistant) -> None:
 
     assert hass.states.get("binary_sensor.test_trend_sensor") is None
     assert hass.states.get("binary_sensor.second_test_trend_sensor")
+
+
+@pytest.mark.parametrize(
+    ("saved_state", "restored_state"),
+    [("on", "on"), ("off", "off"), ("unknown", "unknown")],
+)
+async def test_restore_state(
+    hass: HomeAssistant, saved_state: str, restored_state: str
+) -> None:
+    """Test we restore the trend state."""
+    mock_restore_cache(hass, (State("binary_sensor.test_trend_sensor", saved_state),))
+
+    assert await setup.async_setup_component(
+        hass,
+        "binary_sensor",
+        {
+            "binary_sensor": {
+                "platform": "trend",
+                "sensors": {"test_trend_sensor": {"entity_id": "sensor.test_state"}},
+            }
+        },
+    )
+    await hass.async_block_till_done()
+
+    assert hass.states.get("binary_sensor.test_trend_sensor").state == restored_state