Add support for off_delay to MQTT binary_sensor (#16993)

* Add support for off_delay to MQTT binary_sensor

* Fix debounce, add testcase

* Make off_delay number of seconds instead of timedelta

* Update mqtt.py

* Fix testcase, remove CONF_OFF_DELAY from const.py

tests/components/binary_sensor/test_mqtt.py

@@ -1,6 +1,8 @@
 """The tests for the  MQTT binary sensor platform."""
 import json
 import unittest
+from unittest.mock import Mock
+from datetime import timedelta
 
 import homeassistant.core as ha
 from homeassistant.setup import setup_component, async_setup_component
@@ -10,10 +12,12 @@ from homeassistant.components.mqtt.discovery import async_start
 from homeassistant.const import STATE_OFF, STATE_ON
 from homeassistant.const import EVENT_STATE_CHANGED, STATE_UNAVAILABLE
 
+import homeassistant.util.dt as dt_util
+
 from tests.common import (
     get_test_home_assistant, fire_mqtt_message, async_fire_mqtt_message,
-    mock_component, mock_mqtt_component, async_mock_mqtt_component,
-    MockConfigEntry)
+    fire_time_changed, mock_component, mock_mqtt_component,
+    async_mock_mqtt_component, MockConfigEntry)
 
 
 class TestSensorMQTT(unittest.TestCase):
@@ -22,6 +26,7 @@ class TestSensorMQTT(unittest.TestCase):
     def setUp(self):  # pylint: disable=invalid-name
         """Set up things to be run when tests are started."""
         self.hass = get_test_home_assistant()
+        self.hass.config_entries._async_schedule_save = Mock()
         mock_mqtt_component(self.hass)
 
     def tearDown(self):  # pylint: disable=invalid-name
@@ -209,6 +214,48 @@ class TestSensorMQTT(unittest.TestCase):
         self.hass.block_till_done()
         self.assertEqual(2, len(events))
 
+    def test_off_delay(self):
+        """Test off_delay option."""
+        mock_component(self.hass, 'mqtt')
+        assert setup_component(self.hass, binary_sensor.DOMAIN, {
+            binary_sensor.DOMAIN: {
+                'platform': 'mqtt',
+                'name': 'test',
+                'state_topic': 'test-topic',
+                'payload_on': 'ON',
+                'payload_off': 'OFF',
+                'off_delay': 30,
+                'force_update': True
+            }
+        })
+
+        events = []
+
+        @ha.callback
+        def callback(event):
+            """Verify event got called."""
+            events.append(event)
+
+        self.hass.bus.listen(EVENT_STATE_CHANGED, callback)
+
+        fire_mqtt_message(self.hass, 'test-topic', 'ON')
+        self.hass.block_till_done()
+        state = self.hass.states.get('binary_sensor.test')
+        self.assertEqual(STATE_ON, state.state)
+        self.assertEqual(1, len(events))
+
+        fire_mqtt_message(self.hass, 'test-topic', 'ON')
+        self.hass.block_till_done()
+        state = self.hass.states.get('binary_sensor.test')
+        self.assertEqual(STATE_ON, state.state)
+        self.assertEqual(2, len(events))
+
+        fire_time_changed(self.hass, dt_util.utcnow() + timedelta(seconds=30))
+        self.hass.block_till_done()
+        state = self.hass.states.get('binary_sensor.test')
+        self.assertEqual(STATE_OFF, state.state)
+        self.assertEqual(3, len(events))
+
 
 async def test_unique_id(hass):
     """Test unique id option only creates one sensor per unique_id."""