Improve deCONZ fan platform handling unsupported commands (#41779)

* Improve handling unsupported commands

* Raise valueerror on unsupported speed

* Fix linting

homeassistant/components/deconz/fan.py

@@ -105,7 +105,11 @@ class DeconzFan(DeconzDevice, FanEntity):
 
     async def async_set_speed(self, speed: str) -> None:
         """Set the speed of the fan."""
+        if speed not in SPEEDS:
+            raise ValueError(f"Unsupported speed {speed}")
+
         data = {"speed": SPEEDS[speed]}
+
         await self._device.async_set_state(data)
 
     async def async_turn_on(self, speed: str = None, **kwargs) -> None:

tests/components/deconz/test_fan.py

@@ -1,6 +1,8 @@
 """deCONZ fan platform tests."""
 from copy import deepcopy
 
+import pytest
+
 from homeassistant.components import deconz
 from homeassistant.components.deconz.gateway import get_gateway_from_config_entry
 import homeassistant.components.fan as fan
@@ -165,7 +167,20 @@ async def test_fans(hass):
         await hass.async_block_till_done()
         set_callback.assert_called_with("put", "/lights/1/state", json={"speed": 0})
 
-    # Verify that an unsupported speed gets converted to default speed "medium"
+    # Service set fan speed to unsupported value
+
+    with patch.object(
+        ceiling_fan_device, "_request", return_value=True
+    ) as set_callback, pytest.raises(ValueError):
+        await hass.services.async_call(
+            fan.DOMAIN,
+            fan.SERVICE_SET_SPEED,
+            {"entity_id": "fan.ceiling_fan", fan.ATTR_SPEED: "bad value"},
+            blocking=True,
+        )
+        await hass.async_block_till_done()
+
+    # Events with an unsupported speed gets converted to default speed "medium"
 
     state_changed_event = {
         "t": "event",