Use fan mode when heat/cool is idle in homekit_controller (#128618)

tests/components/homekit_controller/test_climate.py

@@ -6,6 +6,7 @@ from aiohomekit.model import Accessory
 from aiohomekit.model.characteristics import (
     ActivationStateValues,
     CharacteristicsTypes,
+    CurrentFanStateValues,
     CurrentHeaterCoolerStateValues,
     SwingModeValues,
     TargetHeaterCoolerStateValues,
@@ -66,6 +67,9 @@ def create_thermostat_service(accessory: Accessory) -> None:
     char = service.add_char(CharacteristicsTypes.RELATIVE_HUMIDITY_CURRENT)
     char.value = 0
 
+    char = service.add_char(CharacteristicsTypes.FAN_STATE_CURRENT)
+    char.value = 0
+
 
 def create_thermostat_service_min_max(accessory: Accessory) -> None:
     """Define thermostat characteristics."""
@@ -648,6 +652,18 @@ async def test_hvac_mode_vs_hvac_action(
     assert state.state == "heat"
     assert state.attributes["hvac_action"] == "idle"
 
+    # Simulate the fan running while the heat/cool is idle
+    await helper.async_update(
+        ServicesTypes.THERMOSTAT,
+        {
+            CharacteristicsTypes.FAN_STATE_CURRENT: CurrentFanStateValues.ACTIVE,
+        },
+    )
+
+    state = await helper.poll_and_get_state()
+    assert state.state == "heat"
+    assert state.attributes["hvac_action"] == "fan"
+
     # Simulate that current temperature is below target temp
     # Heating might be on and hvac_action currently 'heat'
     await helper.async_update(