Entity registry (#11979)

* Entity#unique_id defaults to None

* Initial commit entity registry

* Clean up unique_id property

* Lint

* Add tests to entity component

* Lint

* Restore some unique ids

* Spelling

* Remove use of IP address for unique ID

* Add tests

* Add tests

* Fix tests

* Add some docs

* Add one more test

* Fix new test…

tests/common.py

@@ -22,6 +22,7 @@ from homeassistant.const import (
     STATE_ON, STATE_OFF, DEVICE_DEFAULT_NAME, EVENT_TIME_CHANGED,
     EVENT_STATE_CHANGED, EVENT_PLATFORM_DISCOVERED, ATTR_SERVICE,
     ATTR_DISCOVERED, SERVER_PORT, EVENT_HOMEASSISTANT_CLOSE)
+from homeassistant.helpers import entity_component, entity_registry
 from homeassistant.components import mqtt, recorder
 from homeassistant.components.http.auth import auth_middleware
 from homeassistant.components.http.const import (
@@ -315,6 +316,14 @@ def mock_component(hass, component):
     hass.config.components.add(component)
 
 
+def mock_registry(hass):
+    """Mock the Entity Registry."""
+    registry = entity_registry.EntityRegistry(hass)
+    registry.entities = {}
+    hass.data[entity_component.DATA_REGISTRY] = registry
+    return registry
+
+
 class MockModule(object):
     """Representation of a fake module."""