Clean up binary_sensor

homeassistant/components/binary_sensor/__init__.py

@@ -61,11 +61,6 @@ class BinarySensorDevice(Entity):
         """Return the state of the binary sensor."""
         return STATE_ON if self.is_on else STATE_OFF
 
-    @property
-    def friendly_state(self):
-        """Return the friendly state of the binary sensor."""
-        return None
-
     @property
     def sensor_class(self):
         """Return the class of this sensor, from SENSOR_CASSES."""
@@ -74,6 +69,9 @@ class BinarySensorDevice(Entity):
     @property
     def state_attributes(self):
         """Return device specific state attributes."""
-        return {
-            'sensor_class': self.sensor_class,
-        }
+        attr = {}
+
+        if self.sensor_class is not None:
+            attr['sensor_class'] = self.sensor_class
+
+        return attr

tests/components/binary_sensor/test_binary_sensor.py

@@ -31,8 +31,7 @@ class TestBinarySensor(unittest.TestCase):
     def test_attributes(self):
         """Test binary sensor attributes."""
         sensor = binary_sensor.BinarySensorDevice()
-        self.assertEqual({'sensor_class': None},
-                         sensor.state_attributes)
+        self.assertEqual({}, sensor.state_attributes)
         with mock.patch('homeassistant.components.binary_sensor.'
                         'BinarySensorDevice.sensor_class',
                         new='motion'):