diff --git a/homeassistant/components/device_tracker/__init__.py b/homeassistant/components/device_tracker/__init__.py
index 8c52f2147b3..b260eccd7d1 100644
--- a/homeassistant/components/device_tracker/__init__.py
+++ b/homeassistant/components/device_tracker/__init__.py
@@ -10,14 +10,19 @@ from datetime import timedelta
 import logging
 import os
 import threading
+from typing import Any, Sequence, Callable
 
-from homeassistant.bootstrap import prepare_setup_platform
+import voluptuous as vol
+
+from homeassistant.bootstrap import (
+    prepare_setup_platform, log_exception)
 from homeassistant.components import group, zone
 from homeassistant.components.discovery import SERVICE_NETGEAR
 from homeassistant.config import load_yaml_config_file
 from homeassistant.exceptions import HomeAssistantError
 from homeassistant.helpers import config_per_platform, discovery
 from homeassistant.helpers.entity import Entity
+from homeassistant.helpers.typing import GPSType, ConfigType, HomeAssistantType
 import homeassistant.helpers.config_validation as cv
 import homeassistant.util as util
 import homeassistant.util.dt as dt_util
@@ -27,8 +32,7 @@ from homeassistant.const import (
     ATTR_GPS_ACCURACY, ATTR_LATITUDE, ATTR_LONGITUDE,
     DEVICE_DEFAULT_NAME, STATE_HOME, STATE_NOT_HOME)
 
-PLATFORM_SCHEMA = cv.PLATFORM_SCHEMA
-DOMAIN = "device_tracker"
+DOMAIN = 'device_tracker'
 DEPENDENCIES = ['zone']
 
 GROUP_NAME_ALL_DEVICES = 'all devices'
@@ -38,21 +42,18 @@ ENTITY_ID_FORMAT = DOMAIN + '.{}'
 
 YAML_DEVICES = 'known_devices.yaml'
 
-CONF_TRACK_NEW = "track_new_devices"
-DEFAULT_CONF_TRACK_NEW = True
+CONF_TRACK_NEW = 'track_new_devices'
+DEFAULT_TRACK_NEW = True
 
 CONF_CONSIDER_HOME = 'consider_home'
 DEFAULT_CONSIDER_HOME = 180  # seconds
 
-CONF_SCAN_INTERVAL = "interval_seconds"
+CONF_SCAN_INTERVAL = 'interval_seconds'
 DEFAULT_SCAN_INTERVAL = 12
 
 CONF_AWAY_HIDE = 'hide_if_away'
 DEFAULT_AWAY_HIDE = False
 
-CONF_HOME_RANGE = 'home_range'
-DEFAULT_HOME_RANGE = 100
-
 SERVICE_SEE = 'see'
 
 ATTR_MAC = 'mac'
@@ -62,23 +63,33 @@ ATTR_LOCATION_NAME = 'location_name'
 ATTR_GPS = 'gps'
 ATTR_BATTERY = 'battery'
 
+PLATFORM_SCHEMA = cv.PLATFORM_SCHEMA.extend({
+    vol.Optional(CONF_SCAN_INTERVAL): cv.positive_int,  # seconds
+}, extra=vol.ALLOW_EXTRA)
+
+_CONFIG_SCHEMA = vol.Schema({DOMAIN: vol.All(cv.ensure_list, [
+    vol.Schema({
+        vol.Optional(CONF_TRACK_NEW): cv.boolean,
+        vol.Optional(CONF_CONSIDER_HOME): cv.positive_int  # seconds
+    }, extra=vol.ALLOW_EXTRA)])}, extra=vol.ALLOW_EXTRA)
+
 DISCOVERY_PLATFORMS = {
     SERVICE_NETGEAR: 'netgear',
 }
 _LOGGER = logging.getLogger(__name__)
 
-# pylint: disable=too-many-arguments
 
-
-def is_on(hass, entity_id=None):
+def is_on(hass: HomeAssistantType, entity_id: str=None):
     """Return the state if any or a specified device is home."""
     entity = entity_id or ENTITY_ID_ALL_DEVICES
 
     return hass.states.is_state(entity, STATE_HOME)
 
 
-def see(hass, mac=None, dev_id=None, host_name=None, location_name=None,
-        gps=None, gps_accuracy=None, battery=None):
+def see(hass: HomeAssistantType, mac: str=None, dev_id: str=None,
+        host_name: str=None, location_name: str=None,
+        gps: GPSType=None, gps_accuracy=None,
+        battery=None):  # pylint: disable=too-many-arguments
     """Call service to notify you see device."""
     data = {key: value for key, value in
             ((ATTR_MAC, mac),
@@ -91,27 +102,24 @@ def see(hass, mac=None, dev_id=None, host_name=None, location_name=None,
     hass.services.call(DOMAIN, SERVICE_SEE, data)
 
 
-def setup(hass, config):
+def setup(hass: HomeAssistantType, config: ConfigType):
     """Setup device tracker."""
     yaml_path = hass.config.path(YAML_DEVICES)
 
-    conf = config.get(DOMAIN, {})
-
-    # Config can be an empty list. In that case, substitute a dict
-    if isinstance(conf, list):
+    try:
+        conf = _CONFIG_SCHEMA(config).get(DOMAIN, [])
+    except vol.Invalid as ex:
+        log_exception(ex, DOMAIN, config)
+        return False
+    else:
         conf = conf[0] if len(conf) > 0 else {}
+        consider_home = timedelta(
+            seconds=conf.get(CONF_CONSIDER_HOME, DEFAULT_CONSIDER_HOME))
+        track_new = conf.get(CONF_TRACK_NEW, DEFAULT_TRACK_NEW)
 
-    consider_home = timedelta(
-        seconds=util.convert(conf.get(CONF_CONSIDER_HOME), int,
-                             DEFAULT_CONSIDER_HOME))
-    track_new = util.convert(conf.get(CONF_TRACK_NEW), bool,
-                             DEFAULT_CONF_TRACK_NEW)
-    home_range = util.convert(conf.get(CONF_HOME_RANGE), int,
-                              DEFAULT_HOME_RANGE)
+    devices = load_config(yaml_path, hass, consider_home)
 
-    devices = load_config(yaml_path, hass, consider_home, home_range)
-    tracker = DeviceTracker(hass, consider_home, track_new, home_range,
-                            devices)
+    tracker = DeviceTracker(hass, consider_home, track_new, devices)
 
     def setup_platform(p_type, p_config, disc_info=None):
         """Setup a device tracker platform."""
@@ -170,30 +178,37 @@ def setup(hass, config):
 class DeviceTracker(object):
     """Representation of a device tracker."""
 
-    def __init__(self, hass, consider_home, track_new, home_range, devices):
+    def __init__(self, hass: HomeAssistantType, consider_home: timedelta,
+                 track_new: bool, devices: Sequence) -> None:
         """Initialize a device tracker."""
         self.hass = hass
         self.devices = {dev.dev_id: dev for dev in devices}
         self.mac_to_dev = {dev.mac: dev for dev in devices if dev.mac}
+        for dev in devices:
+            if self.devices[dev.dev_id] is not dev:
+                _LOGGER.warning('Duplicate device IDs detected %s', dev.dev_id)
+            if dev.mac and self.mac_to_dev[dev.mac] is not dev:
+                _LOGGER.warning('Duplicate device MAC addresses detected %s',
+                                dev.mac)
         self.consider_home = consider_home
         self.track_new = track_new
-        self.home_range = home_range
         self.lock = threading.Lock()
 
         for device in devices:
             if device.track:
                 device.update_ha_state()
 
-        self.group = None
+        self.group = None  # type: group.Group
 
-    def see(self, mac=None, dev_id=None, host_name=None, location_name=None,
-            gps=None, gps_accuracy=None, battery=None):
+    def see(self, mac: str=None, dev_id: str=None, host_name: str=None,
+            location_name: str=None, gps: GPSType=None, gps_accuracy=None,
+            battery: str=None):
         """Notify the device tracker that you see a device."""
         with self.lock:
             if mac is None and dev_id is None:
                 raise HomeAssistantError('Neither mac or device id passed in')
             elif mac is not None:
-                mac = mac.upper()
+                mac = str(mac).upper()
                 device = self.mac_to_dev.get(mac)
                 if not device:
                     dev_id = util.slugify(host_name or '') or util.slugify(mac)
@@ -211,7 +226,7 @@ class DeviceTracker(object):
             # If no device can be found, create it
             dev_id = util.ensure_unique_string(dev_id, self.devices.keys())
             device = Device(
-                self.hass, self.consider_home, self.home_range, self.track_new,
+                self.hass, self.consider_home, self.track_new,
                 dev_id, mac, (host_name or dev_id).replace('_', ' '))
             self.devices[dev_id] = device
             if mac is not None:
@@ -234,7 +249,7 @@ class DeviceTracker(object):
         self.group = group.Group(
             self.hass, GROUP_NAME_ALL_DEVICES, entity_ids, False)
 
-    def update_stale(self, now):
+    def update_stale(self, now: dt_util.dt.datetime):
         """Update stale devices."""
         with self.lock:
             for device in self.devices.values():
@@ -246,19 +261,21 @@ class DeviceTracker(object):
 class Device(Entity):
     """Represent a tracked device."""
 
-    host_name = None
-    location_name = None
-    gps = None
+    host_name = None  # type: str
+    location_name = None  # type: str
+    gps = None  # type: GPSType
     gps_accuracy = 0
-    last_seen = None
-    battery = None
+    last_seen = None  # type: dt_util.dt.datetime
+    battery = None  # type: str
 
     # Track if the last update of this device was HOME.
     last_update_home = False
     _state = STATE_NOT_HOME
 
-    def __init__(self, hass, consider_home, home_range, track, dev_id, mac,
-                 name=None, picture=None, gravatar=None, away_hide=False):
+    def __init__(self, hass: HomeAssistantType, consider_home: timedelta,
+                 track: bool, dev_id: str, mac: str, name: str=None,
+                 picture: str=None, gravatar: str=None,
+                 away_hide: bool=False) -> None:
         """Initialize a device."""
         self.hass = hass
         self.entity_id = ENTITY_ID_FORMAT.format(dev_id)
@@ -267,8 +284,6 @@ class Device(Entity):
         # detected anymore.
         self.consider_home = consider_home
 
-        # Distance in meters
-        self.home_range = home_range
         # Device ID
         self.dev_id = dev_id
         self.mac = mac
@@ -287,13 +302,6 @@ class Device(Entity):
 
         self.away_hide = away_hide
 
-    @property
-    def gps_home(self):
-        """Return if device is within range of home."""
-        distance = max(
-            0, self.hass.config.distance(*self.gps) - self.gps_accuracy)
-        return self.gps is not None and distance <= self.home_range
-
     @property
     def name(self):
         """Return the name of the entity."""
@@ -329,26 +337,24 @@ class Device(Entity):
         """If device should be hidden."""
         return self.away_hide and self.state != STATE_HOME
 
-    def seen(self, host_name=None, location_name=None, gps=None,
-             gps_accuracy=0, battery=None):
+    def seen(self, host_name: str=None, location_name: str=None,
+             gps: GPSType=None, gps_accuracy=0, battery: str=None):
         """Mark the device as seen."""
         self.last_seen = dt_util.utcnow()
         self.host_name = host_name
         self.location_name = location_name
         self.gps_accuracy = gps_accuracy or 0
         self.battery = battery
-        if gps is None:
-            self.gps = None
-        else:
+        self.gps = None
+        if gps is not None:
             try:
-                self.gps = tuple(float(val) for val in gps)
-            except ValueError:
+                self.gps = float(gps[0]), float(gps[1])
+            except (ValueError, TypeError, IndexError):
                 _LOGGER.warning('Could not parse gps value for %s: %s',
                                 self.dev_id, gps)
-                self.gps = None
         self.update()
 
-    def stale(self, now=None):
+    def stale(self, now: dt_util.dt.datetime=None):
         """Return if device state is stale."""
         return self.last_seen and \
             (now or dt_util.utcnow()) - self.last_seen > self.consider_home
@@ -377,32 +383,30 @@ class Device(Entity):
             self.last_update_home = True
 
 
-def load_config(path, hass, consider_home, home_range):
+def load_config(path: str, hass: HomeAssistantType, consider_home: timedelta):
     """Load devices from YAML configuration file."""
-    if not os.path.isfile(path):
-        return []
     try:
         return [
-            Device(hass, consider_home, home_range, device.get('track', False),
+            Device(hass, consider_home, device.get('track', False),
                    str(dev_id).lower(), str(device.get('mac')).upper(),
                    device.get('name'), device.get('picture'),
                    device.get('gravatar'),
                    device.get(CONF_AWAY_HIDE, DEFAULT_AWAY_HIDE))
             for dev_id, device in load_yaml_config_file(path).items()]
-    except HomeAssistantError:
+    except (HomeAssistantError, FileNotFoundError):
         # When YAML file could not be loaded/did not contain a dict
         return []
 
 
-def setup_scanner_platform(hass, config, scanner, see_device):
+def setup_scanner_platform(hass: HomeAssistantType, config: ConfigType,
+                           scanner: Any, see_device: Callable):
     """Helper method to connect scanner-based platform to device tracker."""
-    interval = util.convert(config.get(CONF_SCAN_INTERVAL), int,
-                            DEFAULT_SCAN_INTERVAL)
+    interval = config.get(CONF_SCAN_INTERVAL, DEFAULT_SCAN_INTERVAL)
 
     # Initial scan of each mac we also tell about host name for config
-    seen = set()
+    seen = set()  # type: Any
 
-    def device_tracker_scan(now):
+    def device_tracker_scan(now: dt_util.dt.datetime):
         """Called when interval matches."""
         for mac in scanner.scan_devices():
             if mac in seen:
@@ -418,7 +422,7 @@ def setup_scanner_platform(hass, config, scanner, see_device):
     device_tracker_scan(None)
 
 
-def update_config(path, dev_id, device):
+def update_config(path: str, dev_id: str, device: Device):
     """Add device to YAML configuration file."""
     with open(path, 'a') as out:
         out.write('\n')
@@ -432,8 +436,8 @@ def update_config(path, dev_id, device):
             out.write('  {}: {}\n'.format(key, '' if value is None else value))
 
 
-def get_gravatar_for_email(email):
+def get_gravatar_for_email(email: str):
     """Return an 80px Gravatar for the given email address."""
     import hashlib
-    url = "https://www.gravatar.com/avatar/{}.jpg?s=80&d=wavatar"
+    url = 'https://www.gravatar.com/avatar/{}.jpg?s=80&d=wavatar'
     return url.format(hashlib.md5(email.encode('utf-8').lower()).hexdigest())
diff --git a/homeassistant/components/device_tracker/bluetooth_le_tracker.py b/homeassistant/components/device_tracker/bluetooth_le_tracker.py
index 7784a2326d8..6576f46bad7 100644
--- a/homeassistant/components/device_tracker/bluetooth_le_tracker.py
+++ b/homeassistant/components/device_tracker/bluetooth_le_tracker.py
@@ -63,7 +63,7 @@ def setup_scanner(hass, config, see):
     # Load all known devices.
     # We just need the devices so set consider_home and home range
     # to 0
-    for device in load_config(yaml_path, hass, 0, 0):
+    for device in load_config(yaml_path, hass, 0):
         # check if device is a valid bluetooth device
         if device.mac and device.mac[:3].upper() == BLE_PREFIX:
             if device.track:
diff --git a/homeassistant/components/device_tracker/bluetooth_tracker.py b/homeassistant/components/device_tracker/bluetooth_tracker.py
index 70fefbca1b7..298eddc4bc4 100644
--- a/homeassistant/components/device_tracker/bluetooth_tracker.py
+++ b/homeassistant/components/device_tracker/bluetooth_tracker.py
@@ -45,7 +45,7 @@ def setup_scanner(hass, config, see):
     # Load all known devices.
     # We just need the devices so set consider_home and home range
     # to 0
-    for device in load_config(yaml_path, hass, 0, 0):
+    for device in load_config(yaml_path, hass, 0):
         # check if device is a valid bluetooth device
         if device.mac and device.mac[:3].upper() == BT_PREFIX:
             if device.track:
diff --git a/homeassistant/helpers/typing.py b/homeassistant/helpers/typing.py
index 6eb53f14493..24774ac29da 100644
--- a/homeassistant/helpers/typing.py
+++ b/homeassistant/helpers/typing.py
@@ -1,24 +1,13 @@
 """Typing Helpers for Home-Assistant."""
-from typing import Dict, Any
+from typing import Dict, Any, Tuple
 
-# NOTE: NewType added to typing in 3.5.2 in June, 2016; Since 3.5.2 includes
-#       security fixes everyone on 3.5 should upgrade "soon"
-try:
-    from typing import NewType
-except ImportError:
-    NewType = None
+import homeassistant.core
 
 # pylint: disable=invalid-name
-if NewType:
-    ConfigType = NewType('ConfigType', Dict[str, Any])
 
-    # Custom type for recorder Queries
-    QueryType = NewType('QueryType', Any)
+GPSType = Tuple[float, float]
+ConfigType = Dict[str, Any]
+HomeAssistantType = homeassistant.core.HomeAssistant
 
-# Duplicates for 3.5.1
-# pylint: disable=invalid-name
-else:
-    ConfigType = Dict[str, Any]  # type: ignore
-
-    # Custom type for recorder Queries
-    QueryType = Any  # type: ignore
+# Custom type for recorder Queries
+QueryType = Any
diff --git a/homeassistant/util/__init__.py b/homeassistant/util/__init__.py
index 032588f6cba..c5df3834e72 100644
--- a/homeassistant/util/__init__.py
+++ b/homeassistant/util/__init__.py
@@ -12,7 +12,7 @@ import string
 from functools import wraps
 from types import MappingProxyType
 
-from typing import Any, Optional, TypeVar, Callable, Sequence
+from typing import Any, Optional, TypeVar, Callable, Sequence, KeysView, Union
 
 from .dt import as_local, utcnow
 
@@ -63,8 +63,8 @@ def convert(value: T, to_type: Callable[[T], U],
         return default
 
 
-def ensure_unique_string(preferred_string: str,
-                         current_strings: Sequence[str]) -> str:
+def ensure_unique_string(preferred_string: str, current_strings:
+                         Union[Sequence[str], KeysView[str]]) -> str:
     """Return a string that is not present in current_strings.
 
     If preferred string exists will append _2, _3, ..
diff --git a/tests/common.py b/tests/common.py
index 5d1f485d7fe..e51e4ba048a 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -7,7 +7,7 @@ from io import StringIO
 import logging
 
 from homeassistant import core as ha, loader
-from homeassistant.bootstrap import _setup_component
+from homeassistant.bootstrap import setup_component
 from homeassistant.helpers.entity import ToggleEntity
 from homeassistant.util.unit_system import METRIC_SYSTEM
 import homeassistant.util.dt as date_util
@@ -137,15 +137,15 @@ def mock_http_component(hass):
     hass.config.components.append('http')
 
 
-@mock.patch('homeassistant.components.mqtt.MQTT')
-def mock_mqtt_component(hass, mock_mqtt):
+def mock_mqtt_component(hass):
     """Mock the MQTT component."""
-    _setup_component(hass, mqtt.DOMAIN, {
-        mqtt.DOMAIN: {
-            mqtt.CONF_BROKER: 'mock-broker',
-        }
-    })
-    return mock_mqtt
+    with mock.patch('homeassistant.components.mqtt.MQTT') as mock_mqtt:
+        setup_component(hass, mqtt.DOMAIN, {
+            mqtt.DOMAIN: {
+                mqtt.CONF_BROKER: 'mock-broker',
+            }
+        })
+        return mock_mqtt
 
 
 class MockModule(object):
diff --git a/tests/components/device_tracker/test_init.py b/tests/components/device_tracker/test_init.py
index c6721b8c8cc..7353cbae0d8 100644
--- a/tests/components/device_tracker/test_init.py
+++ b/tests/components/device_tracker/test_init.py
@@ -1,10 +1,10 @@
 """The tests for the device tracker component."""
 # pylint: disable=protected-access,too-many-public-methods
+import logging
 import unittest
 from unittest.mock import patch
 from datetime import datetime, timedelta
 import os
-import tempfile
 
 from homeassistant.loader import get_component
 import homeassistant.util.dt as dt_util
@@ -12,13 +12,21 @@ from homeassistant.const import (
     ATTR_ENTITY_ID, ATTR_ENTITY_PICTURE, ATTR_FRIENDLY_NAME, ATTR_HIDDEN,
     STATE_HOME, STATE_NOT_HOME, CONF_PLATFORM)
 import homeassistant.components.device_tracker as device_tracker
+from homeassistant.exceptions import HomeAssistantError
 
 from tests.common import (
-    get_test_home_assistant, fire_time_changed, fire_service_discovered)
+    get_test_home_assistant, fire_time_changed, fire_service_discovered,
+    patch_yaml_files)
+
+TEST_PLATFORM = {device_tracker.DOMAIN: {CONF_PLATFORM: 'test'}}
+
+_LOGGER = logging.getLogger(__name__)
 
 
 class TestComponentsDeviceTracker(unittest.TestCase):
     """Test the Device tracker."""
+    hass = None  # HomeAssistant
+    yaml_devices = None  # type: str
 
     def setUp(self):  # pylint: disable=invalid-name
         """Setup things to be run when tests are started."""
@@ -48,27 +56,28 @@ class TestComponentsDeviceTracker(unittest.TestCase):
 
     def test_reading_broken_yaml_config(self):  # pylint: disable=no-self-use
         """Test when known devices contains invalid data."""
-        with tempfile.NamedTemporaryFile() as fpt:
-            # file is empty
-            assert device_tracker.load_config(fpt.name, None, False, 0) == []
-
-            fpt.write('100'.encode('utf-8'))
-            fpt.flush()
-
-            # file contains a non-dict format
-            assert device_tracker.load_config(fpt.name, None, False, 0) == []
+        files = {'empty.yaml': '',
+                 'bad.yaml': '100',
+                 'ok.yaml': 'my_device:\n  name: Device'}
+        with patch_yaml_files(files):
+            # File is empty
+            assert device_tracker.load_config('empty.yaml', None, False) == []
+            # File contains a non-dict format
+            assert device_tracker.load_config('bad.yaml', None, False) == []
+            # A file that works fine
+            assert len(device_tracker.load_config('ok.yaml', None, False)) == 1
 
     def test_reading_yaml_config(self):
         """Test the rendering of the YAML configuration."""
         dev_id = 'test'
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id,
+            self.hass, timedelta(seconds=180), True, dev_id,
             'AB:CD:EF:GH:IJ', 'Test name', picture='http://test.picture',
             away_hide=True)
         device_tracker.update_config(self.yaml_devices, dev_id, device)
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
         config = device_tracker.load_config(self.yaml_devices, self.hass,
-                                            device.consider_home, 0)[0]
+                                            device.consider_home)[0]
         self.assertEqual(device.dev_id, config.dev_id)
         self.assertEqual(device.track, config.track)
         self.assertEqual(device.mac, config.mac)
@@ -76,12 +85,45 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         self.assertEqual(device.away_hide, config.away_hide)
         self.assertEqual(device.consider_home, config.consider_home)
 
+    @patch('homeassistant.components.device_tracker._LOGGER.warning')
+    def test_track_with_duplicate_mac_dev_id(self, mock_warning):  \
+            # pylint: disable=invalid-name
+        """Test adding duplicate MACs or device IDs to DeviceTracker."""
+
+        devices = [
+            device_tracker.Device(self.hass, True, True, 'my_device', 'AB:01',
+                                  'My device', None, None, False),
+            device_tracker.Device(self.hass, True, True, 'your_device',
+                                  'AB:01', 'Your device', None, None, False)]
+        device_tracker.DeviceTracker(self.hass, False, True, devices)
+        _LOGGER.debug(mock_warning.call_args_list)
+        assert mock_warning.call_count == 1, \
+            "The only warning call should be duplicates (check DEBUG)"
+        args, _ = mock_warning.call_args
+        assert 'Duplicate device MAC' in args[0], \
+            'Duplicate MAC warning expected'
+
+        mock_warning.reset_mock()
+        devices = [
+            device_tracker.Device(self.hass, True, True, 'my_device',
+                                  'AB:01', 'My device', None, None, False),
+            device_tracker.Device(self.hass, True, True, 'my_device',
+                                  None, 'Your device', None, None, False)]
+        device_tracker.DeviceTracker(self.hass, False, True, devices)
+
+        _LOGGER.debug(mock_warning.call_args_list)
+        assert mock_warning.call_count == 1, \
+            "The only warning call should be duplicates (check DEBUG)"
+        args, _ = mock_warning.call_args
+        assert 'Duplicate device IDs' in args[0], \
+            'Duplicate device IDs warning expected'
+
     def test_setup_without_yaml_file(self):
         """Test with no YAML file."""
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
-    # pylint: disable=invalid-name
-    def test_adding_unknown_device_to_config(self):
+    def test_adding_unknown_device_to_config(self): \
+            # pylint: disable=invalid-name
         """Test the adding of unknown devices to configuration file."""
         scanner = get_component('device_tracker.test').SCANNER
         scanner.reset()
@@ -90,7 +132,7 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         self.assertTrue(device_tracker.setup(self.hass, {
             device_tracker.DOMAIN: {CONF_PLATFORM: 'test'}}))
         config = device_tracker.load_config(self.yaml_devices, self.hass,
-                                            timedelta(seconds=0), 0)
+                                            timedelta(seconds=0))
         assert len(config) == 1
         assert config[0].dev_id == 'dev1'
         assert config[0].track
@@ -99,7 +141,7 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         """Test the Gravatar generation."""
         dev_id = 'test'
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id,
+            self.hass, timedelta(seconds=180), True, dev_id,
             'AB:CD:EF:GH:IJ', 'Test name', gravatar='test@example.com')
         gravatar_url = ("https://www.gravatar.com/avatar/"
                         "55502f40dc8b7c769880b10874abc9d0.jpg?s=80&d=wavatar")
@@ -109,7 +151,7 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         """Test that Gravatar overrides picture."""
         dev_id = 'test'
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id,
+            self.hass, timedelta(seconds=180), True, dev_id,
             'AB:CD:EF:GH:IJ', 'Test name', picture='http://test.picture',
             gravatar='test@example.com')
         gravatar_url = ("https://www.gravatar.com/avatar/"
@@ -122,8 +164,8 @@ class TestComponentsDeviceTracker(unittest.TestCase):
 
         with patch.dict(device_tracker.DISCOVERY_PLATFORMS, {'test': 'test'}):
             with patch.object(scanner, 'scan_devices') as mock_scan:
-                self.assertTrue(device_tracker.setup(self.hass, {
-                    device_tracker.DOMAIN: {CONF_PLATFORM: 'test'}}))
+                self.assertTrue(device_tracker.setup(self.hass,
+                                                     TEST_PLATFORM))
                 fire_service_discovered(self.hass, 'test', {})
                 self.assertTrue(mock_scan.called)
 
@@ -139,9 +181,9 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         with patch('homeassistant.components.device_tracker.dt_util.utcnow',
                    return_value=register_time):
             self.assertTrue(device_tracker.setup(self.hass, {
-                'device_tracker': {
-                    'platform': 'test',
-                    'consider_home': 59,
+                device_tracker.DOMAIN: {
+                    CONF_PLATFORM: 'test',
+                    device_tracker.CONF_CONSIDER_HOME: 59,
                 }}))
 
         self.assertEqual(STATE_HOME,
@@ -165,11 +207,11 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         picture = 'http://placehold.it/200x200'
 
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id, None,
+            self.hass, timedelta(seconds=180), True, dev_id, None,
             friendly_name, picture, away_hide=True)
         device_tracker.update_config(self.yaml_devices, dev_id, device)
 
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
         attrs = self.hass.states.get(entity_id).attributes
 
@@ -181,15 +223,14 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         dev_id = 'test_entity'
         entity_id = device_tracker.ENTITY_ID_FORMAT.format(dev_id)
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id, None,
+            self.hass, timedelta(seconds=180), True, dev_id, None,
             away_hide=True)
         device_tracker.update_config(self.yaml_devices, dev_id, device)
 
         scanner = get_component('device_tracker.test').SCANNER
         scanner.reset()
 
-        self.assertTrue(device_tracker.setup(self.hass, {
-            device_tracker.DOMAIN: {CONF_PLATFORM: 'test'}}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
         self.assertTrue(self.hass.states.get(entity_id)
                         .attributes.get(ATTR_HIDDEN))
@@ -199,15 +240,14 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         dev_id = 'test_entity'
         entity_id = device_tracker.ENTITY_ID_FORMAT.format(dev_id)
         device = device_tracker.Device(
-            self.hass, timedelta(seconds=180), 0, True, dev_id, None,
+            self.hass, timedelta(seconds=180), True, dev_id, None,
             away_hide=True)
         device_tracker.update_config(self.yaml_devices, dev_id, device)
 
         scanner = get_component('device_tracker.test').SCANNER
         scanner.reset()
 
-        self.assertTrue(device_tracker.setup(self.hass, {
-            device_tracker.DOMAIN: {CONF_PLATFORM: 'test'}}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
         state = self.hass.states.get(device_tracker.ENTITY_ID_ALL_DEVICES)
         self.assertIsNotNone(state)
@@ -217,40 +257,31 @@ class TestComponentsDeviceTracker(unittest.TestCase):
 
     @patch('homeassistant.components.device_tracker.DeviceTracker.see')
     def test_see_service(self, mock_see):
-        """Test the see service."""
-        self.assertTrue(device_tracker.setup(self.hass, {}))
-        mac = 'AB:CD:EF:GH'
-        dev_id = 'some_device'
-        host_name = 'example.com'
-        location_name = 'Work'
-        gps = [.3, .8]
-
-        device_tracker.see(self.hass, mac, dev_id, host_name, location_name,
-                           gps)
-
-        self.hass.pool.block_till_done()
-
-        mock_see.assert_called_once_with(
-            mac=mac, dev_id=dev_id, host_name=host_name,
-            location_name=location_name, gps=gps)
-
-    @patch('homeassistant.components.device_tracker.DeviceTracker.see')
-    def test_see_service_unicode_dev_id(self, mock_see):
         """Test the see service with a unicode dev_id and NO MAC."""
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
         params = {
-            'dev_id': chr(233),  # e' acute accent from icloud
+            'dev_id': 'some_device',
             'host_name': 'example.com',
             'location_name': 'Work',
             'gps': [.3, .8]
         }
         device_tracker.see(self.hass, **params)
         self.hass.pool.block_till_done()
+        assert mock_see.call_count == 1
         mock_see.assert_called_once_with(**params)
 
-    def test_not_write_duplicate_yaml_keys(self):
+        mock_see.reset_mock()
+        params['dev_id'] += chr(233)  # e' acute accent from icloud
+
+        device_tracker.see(self.hass, **params)
+        self.hass.pool.block_till_done()
+        assert mock_see.call_count == 1
+        mock_see.assert_called_once_with(**params)
+
+    def test_not_write_duplicate_yaml_keys(self): \
+            # pylint: disable=invalid-name
         """Test that the device tracker will not generate invalid YAML."""
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
         device_tracker.see(self.hass, 'mac_1', host_name='hello')
         device_tracker.see(self.hass, 'mac_2', host_name='hello')
@@ -258,15 +289,46 @@ class TestComponentsDeviceTracker(unittest.TestCase):
         self.hass.pool.block_till_done()
 
         config = device_tracker.load_config(self.yaml_devices, self.hass,
-                                            timedelta(seconds=0), 0)
+                                            timedelta(seconds=0))
         assert len(config) == 2
 
-    def test_not_allow_invalid_dev_id(self):
+    def test_not_allow_invalid_dev_id(self):  # pylint: disable=invalid-name
         """Test that the device tracker will not allow invalid dev ids."""
-        self.assertTrue(device_tracker.setup(self.hass, {}))
+        self.assertTrue(device_tracker.setup(self.hass, TEST_PLATFORM))
 
         device_tracker.see(self.hass, dev_id='hello-world')
 
         config = device_tracker.load_config(self.yaml_devices, self.hass,
-                                            timedelta(seconds=0), 0)
+                                            timedelta(seconds=0))
         assert len(config) == 0
+
+    @patch('homeassistant.components.device_tracker._LOGGER.warning')
+    def test_see_failures(self, mock_warning):
+        """Test that the device tracker see failures."""
+        tracker = device_tracker.DeviceTracker(
+            self.hass, timedelta(seconds=60), 0, [])
+
+        # MAC is not a string (but added)
+        tracker.see(mac=567, host_name="Number MAC")
+
+        # No device id or MAC(not added)
+        with self.assertRaises(HomeAssistantError):
+            tracker.see()
+        assert mock_warning.call_count == 0
+
+        # Ignore gps on invalid GPS (both added & warnings)
+        tracker.see(mac='mac_1_bad_gps', gps=1)
+        tracker.see(mac='mac_2_bad_gps', gps=[1])
+        tracker.see(mac='mac_3_bad_gps', gps='gps')
+        config = device_tracker.load_config(self.yaml_devices, self.hass,
+                                            timedelta(seconds=0))
+        assert mock_warning.call_count == 3
+
+        assert len(config) == 4
+
+    @patch('homeassistant.components.device_tracker.log_exception')
+    def test_config_failure(self, mock_ex):
+        """Test that the device tracker see failures."""
+        device_tracker.setup(self.hass, {device_tracker.DOMAIN: {
+            device_tracker.CONF_CONSIDER_HOME: -1}})
+        assert mock_ex.call_count == 1
diff --git a/tests/components/device_tracker/test_locative.py b/tests/components/device_tracker/test_locative.py
index 427980be5f1..7c018eaa69a 100644
--- a/tests/components/device_tracker/test_locative.py
+++ b/tests/components/device_tracker/test_locative.py
@@ -8,17 +8,19 @@ import requests
 from homeassistant import bootstrap, const
 import homeassistant.components.device_tracker as device_tracker
 import homeassistant.components.http as http
+from homeassistant.const import CONF_PLATFORM
 
 from tests.common import get_test_home_assistant, get_test_instance_port
 
 SERVER_PORT = get_test_instance_port()
 HTTP_BASE_URL = "http://127.0.0.1:{}".format(SERVER_PORT)
 
-hass = None
+hass = None  # pylint: disable=invalid-name
 
 
-def _url(data={}):
+def _url(data=None):
     """Helper method to generate URLs."""
+    data = data or {}
     data = "&".join(["{}={}".format(name, value) for
                      name, value in data.items()])
     return "{}{}locative?{}".format(HTTP_BASE_URL, const.URL_API, data)
@@ -26,7 +28,7 @@ def _url(data={}):
 
 def setUpModule():   # pylint: disable=invalid-name
     """Initalize a Home Assistant server."""
-    global hass
+    global hass    # pylint: disable=invalid-name
 
     hass = get_test_home_assistant()
     bootstrap.setup_component(hass, http.DOMAIN, {
@@ -38,7 +40,7 @@ def setUpModule():   # pylint: disable=invalid-name
     # Set up device tracker
     bootstrap.setup_component(hass, device_tracker.DOMAIN, {
         device_tracker.DOMAIN: {
-            'platform': 'locative'
+            CONF_PLATFORM: 'locative'
         }
     })
 
diff --git a/tests/components/device_tracker/test_mqtt.py b/tests/components/device_tracker/test_mqtt.py
index 139316a35bf..321ab16ac3f 100644
--- a/tests/components/device_tracker/test_mqtt.py
+++ b/tests/components/device_tracker/test_mqtt.py
@@ -1,5 +1,7 @@
 """The tests for the MQTT device tracker platform."""
 import unittest
+from unittest.mock import patch
+import logging
 import os
 
 from homeassistant.bootstrap import _setup_component
@@ -9,6 +11,8 @@ from homeassistant.const import CONF_PLATFORM
 from tests.common import (
     get_test_home_assistant, mock_mqtt_component, fire_mqtt_message)
 
+_LOGGER = logging.getLogger(__name__)
+
 
 class TestComponentsDeviceTrackerMQTT(unittest.TestCase):
     """Test MQTT device tracker platform."""
@@ -25,6 +29,27 @@ class TestComponentsDeviceTrackerMQTT(unittest.TestCase):
         except FileNotFoundError:
             pass
 
+    def test_ensure_device_tracker_platform_validation(self): \
+            # pylint: disable=invalid-name
+        """Test if platform validation was done."""
+        def mock_setup_scanner(hass, config, see):
+            """Check that Qos was added by validation."""
+            self.assertTrue('qos' in config)
+
+        with patch('homeassistant.components.device_tracker.mqtt.'
+                   'setup_scanner', side_effect=mock_setup_scanner) as mock_sp:
+
+            dev_id = 'paulus'
+            topic = '/location/paulus'
+            self.hass.config.components = ['mqtt', 'zone']
+            assert _setup_component(self.hass, device_tracker.DOMAIN, {
+                device_tracker.DOMAIN: {
+                    CONF_PLATFORM: 'mqtt',
+                    'devices': {dev_id: topic}
+                }
+            })
+            assert mock_sp.call_count == 1
+
     def test_new_message(self):
         """Test new message."""
         dev_id = 'paulus'
diff --git a/tests/components/test_device_sun_light_trigger.py b/tests/components/test_device_sun_light_trigger.py
index ff134465174..88c0bae60ec 100644
--- a/tests/components/test_device_sun_light_trigger.py
+++ b/tests/components/test_device_sun_light_trigger.py
@@ -22,12 +22,12 @@ def setUpModule():   # pylint: disable=invalid-name
     """Write a device tracker known devices file to be used."""
     device_tracker.update_config(
         KNOWN_DEV_YAML_PATH, 'device_1', device_tracker.Device(
-            None, None, None, True, 'device_1', 'DEV1',
+            None, None, True, 'device_1', 'DEV1',
             picture='http://example.com/dev1.jpg'))
 
     device_tracker.update_config(
         KNOWN_DEV_YAML_PATH, 'device_2', device_tracker.Device(
-            None, None, None, True, 'device_2', 'DEV2',
+            None, None, True, 'device_2', 'DEV2',
             picture='http://example.com/dev2.jpg'))
 
 
@@ -83,7 +83,8 @@ class TestDeviceSunLightTrigger(unittest.TestCase):
 
         self.assertTrue(light.is_on(self.hass))
 
-    def test_lights_turn_off_when_everyone_leaves(self):
+    def test_lights_turn_off_when_everyone_leaves(self): \
+            # pylint: disable=invalid-name
         """Test lights turn off when everyone leaves the house."""
         light.turn_on(self.hass)
 
@@ -99,7 +100,8 @@ class TestDeviceSunLightTrigger(unittest.TestCase):
 
         self.assertFalse(light.is_on(self.hass))
 
-    def test_lights_turn_on_when_coming_home_after_sun_set(self):
+    def test_lights_turn_on_when_coming_home_after_sun_set(self): \
+            # pylint: disable=invalid-name
         """Test lights turn on when coming home after sun set."""
         light.turn_off(self.hass)
         ensure_sun_set(self.hass)