diff --git a/homeassistant/components/demo/binary_sensor.py b/homeassistant/components/demo/binary_sensor.py
index 584c0cf88f1..ee718e85cc0 100644
--- a/homeassistant/components/demo/binary_sensor.py
+++ b/homeassistant/components/demo/binary_sensor.py
@@ -61,7 +61,7 @@ class DemoBinarySensor(BinarySensorEntity):
         self._unique_id = unique_id
         self._attr_name = name
         self._state = state
-        self._sensor_type = device_class
+        self._attr_device_class = device_class
 
     @property
     def device_info(self) -> DeviceInfo:
@@ -79,11 +79,6 @@ class DemoBinarySensor(BinarySensorEntity):
         """Return the unique id."""
         return self._unique_id
 
-    @property
-    def device_class(self) -> BinarySensorDeviceClass:
-        """Return the class of this sensor."""
-        return self._sensor_type
-
     @property
     def is_on(self) -> bool:
         """Return true if the binary sensor is on."""
diff --git a/homeassistant/components/demo/cover.py b/homeassistant/components/demo/cover.py
index fbb8a171516..845bd9976a3 100644
--- a/homeassistant/components/demo/cover.py
+++ b/homeassistant/components/demo/cover.py
@@ -85,7 +85,7 @@ class DemoCover(CoverEntity):
         self._unique_id = unique_id
         self._attr_name = name
         self._position = position
-        self._device_class = device_class
+        self._attr_device_class = device_class
         self._supported_features = supported_features
         self._set_position: int | None = None
         self._set_tilt_position: int | None = None
@@ -142,11 +142,6 @@ class DemoCover(CoverEntity):
         """Return if the cover is opening."""
         return self._is_opening
 
-    @property
-    def device_class(self) -> CoverDeviceClass | None:
-        """Return the class of this device, from component DEVICE_CLASSES."""
-        return self._device_class
-
     @property
     def supported_features(self) -> int:
         """Flag supported features."""
diff --git a/homeassistant/components/demo/media_player.py b/homeassistant/components/demo/media_player.py
index 8dbf059c2ca..e0c05e853c1 100644
--- a/homeassistant/components/demo/media_player.py
+++ b/homeassistant/components/demo/media_player.py
@@ -120,7 +120,7 @@ class AbstractDemoPlayer(MediaPlayerEntity):
         self._shuffle = False
         self._sound_mode_list = SOUND_MODE_LIST
         self._sound_mode = DEFAULT_SOUND_MODE
-        self._device_class = device_class
+        self._attr_device_class = device_class
 
     @property
     def state(self) -> str:
@@ -152,11 +152,6 @@ class AbstractDemoPlayer(MediaPlayerEntity):
         """Return a list of available sound modes."""
         return self._sound_mode_list
 
-    @property
-    def device_class(self) -> MediaPlayerDeviceClass | None:
-        """Return the device class of the media player."""
-        return self._device_class
-
     def turn_on(self) -> None:
         """Turn the media player on."""
         self._player_state = MediaPlayerState.PLAYING
@@ -427,12 +422,11 @@ class DemoTVShowPlayer(AbstractDemoPlayer):
 
     # We only implement the methods that we support
 
-    _attr_device_class = MediaPlayerDeviceClass.TV
     _attr_media_content_type = MediaType.TVSHOW
 
     def __init__(self) -> None:
         """Initialize the demo device."""
-        super().__init__("Lounge room")
+        super().__init__("Lounge room", MediaPlayerDeviceClass.TV)
         self._cur_episode = 1
         self._episode_count = 13
         self._source = "dvd"
diff --git a/tests/components/google_assistant/__init__.py b/tests/components/google_assistant/__init__.py
index 423bb1b55d7..2122818bbb4 100644
--- a/tests/components/google_assistant/__init__.py
+++ b/tests/components/google_assistant/__init__.py
@@ -221,7 +221,7 @@ DEMO_DEVICES = [
             "action.devices.traits.TransportControl",
             "action.devices.traits.MediaState",
         ],
-        "type": "action.devices.types.SETTOP",
+        "type": "action.devices.types.TV",
         "willReportState": False,
     },
     {