Allow source sensor to be changed in threshold helper (#119157)

* Allow source sensor to be changed in threshold helper

* Make sure old device link is removed on entry change

* Add test case for changed association

tests/components/threshold/test_init.py

@@ -4,7 +4,7 @@ import pytest
 
 from homeassistant.components.threshold.const import DOMAIN
 from homeassistant.core import HomeAssistant
-from homeassistant.helpers import entity_registry as er
+from homeassistant.helpers import device_registry as dr, entity_registry as er
 
 from tests.common import MockConfigEntry
 
@@ -44,6 +44,7 @@ async def test_setup_and_remove_config_entry(
 
     # Check the platform is setup correctly
     state = hass.states.get(threshold_entity_id)
+    assert state
     assert state.state == "on"
     assert state.attributes["entity_id"] == input_sensor
     assert state.attributes["hysteresis"] == 0.0
@@ -60,3 +61,64 @@ async def test_setup_and_remove_config_entry(
     # Check the state and entity registry entry are removed
     assert hass.states.get(threshold_entity_id) is None
     assert entity_registry.async_get(threshold_entity_id) is None
+
+
+@pytest.mark.parametrize("platform", ["sensor"])
+async def test_entry_changed(hass: HomeAssistant, platform) -> None:
+    """Test reconfiguring."""
+
+    device_registry = dr.async_get(hass)
+    entity_registry = er.async_get(hass)
+
+    def _create_mock_entity(domain: str, name: str) -> er.RegistryEntry:
+        config_entry = MockConfigEntry(
+            data={},
+            domain="test",
+            title=f"{name}",
+        )
+        config_entry.add_to_hass(hass)
+        device_entry = device_registry.async_get_or_create(
+            identifiers={("test", name)}, config_entry_id=config_entry.entry_id
+        )
+        return entity_registry.async_get_or_create(
+            domain, "test", name, suggested_object_id=name, device_id=device_entry.id
+        )
+
+    def _get_device_config_entries(entry: er.RegistryEntry) -> set[str]:
+        assert entry.device_id
+        device = device_registry.async_get(entry.device_id)
+        assert device
+        return device.config_entries
+
+    # Set up entities, with backing devices and config entries
+    run1_entry = _create_mock_entity("sensor", "initial")
+    run2_entry = _create_mock_entity("sensor", "changed")
+
+    # Setup the config entry
+    config_entry = MockConfigEntry(
+        data={},
+        domain=DOMAIN,
+        options={
+            "entity_id": "sensor.initial",
+            "hysteresis": 0.0,
+            "lower": -2.0,
+            "name": "My threshold",
+            "upper": None,
+        },
+        title="My integration",
+    )
+    config_entry.add_to_hass(hass)
+    assert await hass.config_entries.async_setup(config_entry.entry_id)
+    await hass.async_block_till_done()
+
+    assert config_entry.entry_id in _get_device_config_entries(run1_entry)
+    assert config_entry.entry_id not in _get_device_config_entries(run2_entry)
+
+    hass.config_entries.async_update_entry(
+        config_entry, options={**config_entry.options, "entity_id": "sensor.changed"}
+    )
+    await hass.async_block_till_done()
+
+    # Check that the config entry association has updated
+    assert config_entry.entry_id not in _get_device_config_entries(run1_entry)
+    assert config_entry.entry_id in _get_device_config_entries(run2_entry)