Fix derivative sensor spike after total_increasing reset

homeassistant/components/derivative/sensor.py

@@ -546,6 +546,11 @@ class DerivativeSensor(RestoreSensor, SensorEntity):
                     "%s: Dropping sample as source total_increasing sensor decreased",
                     self.entity_id,
                 )
+                self._last_valid_state_time = (
+                    new_state.state,
+                    new_timestamp,
+                )
+                self._write_native_value(Decimal(0))
                 return
 
             # add latest derivative to the window list

tests/components/derivative/test_sensor.py

@@ -864,8 +864,8 @@ async def test_total_increasing_reset(hass: HomeAssistant) -> None:
     """Test derivative with total_increasing input where it should ignore the reset."""
     times = [0, 20, 30, 35, 40, 50, 60]
     values = [0, 10, 30, 40, 0, 10, 40]
-    expected_times = [0, 20, 30, 35, 50, 60]
-    expected_values = ["0.00", "0.50", "2.00", "2.00", "1.00", "3.00"]
+    expected_times = [0, 20, 30, 35, 40, 50, 60]
+    expected_values = ["0.00", "0.50", "2.00", "2.00", "0.00", "1.00", "3.00"]
 
     _config, entity_id = await _setup_sensor(hass, {"unit_time": UnitOfTime.SECONDS})