diff --git a/homeassistant/helpers/config_validation.py b/homeassistant/helpers/config_validation.py
index 7ec6d177178..bd5d85230c5 100644
--- a/homeassistant/helpers/config_validation.py
+++ b/homeassistant/helpers/config_validation.py
@@ -6,6 +6,7 @@ import re
 from datetime import (timedelta, datetime as datetime_sys,
                       time as time_sys, date as date_sys)
 from socket import _GLOBAL_DEFAULT_TIMEOUT
+from numbers import Number
 from typing import Any, Union, TypeVar, Callable, Sequence, Dict, Optional
 from urllib.parse import urlparse
 from uuid import UUID
@@ -81,14 +82,17 @@ def has_at_most_one_key(*keys: str) -> Callable:
 
 def boolean(value: Any) -> bool:
     """Validate and coerce a boolean value."""
+    if isinstance(value, bool):
+        return value
     if isinstance(value, str):
-        value = value.lower()
+        value = value.lower().strip()
         if value in ('1', 'true', 'yes', 'on', 'enable'):
             return True
         if value in ('0', 'false', 'no', 'off', 'disable'):
             return False
-        raise vol.Invalid('invalid boolean value {}'.format(value))
-    return bool(value)
+    elif isinstance(value, Number):
+        return value != 0
+    raise vol.Invalid('invalid boolean value {}'.format(value))
 
 
 def isdevice(value):
diff --git a/tests/components/demo/test_climate.py b/tests/components/demo/test_climate.py
index 3166b2d3158..444b053fc19 100644
--- a/tests/components/demo/test_climate.py
+++ b/tests/components/demo/test_climate.py
@@ -203,7 +203,8 @@ class TestDemoClimate(unittest.TestCase):
         """Test setting the away mode without required attribute."""
         state = self.hass.states.get(ENTITY_CLIMATE)
         assert 'on' == state.attributes.get('away_mode')
-        common.set_away_mode(self.hass, None, ENTITY_CLIMATE)
+        with pytest.raises(vol.Invalid):
+            common.set_away_mode(self.hass, None, ENTITY_CLIMATE)
         self.hass.block_till_done()
         assert 'on' == state.attributes.get('away_mode')
 
@@ -246,7 +247,8 @@ class TestDemoClimate(unittest.TestCase):
         """Test setting the auxiliary heater without required attribute."""
         state = self.hass.states.get(ENTITY_CLIMATE)
         assert 'off' == state.attributes.get('aux_heat')
-        common.set_aux_heat(self.hass, None, ENTITY_CLIMATE)
+        with pytest.raises(vol.Invalid):
+            common.set_aux_heat(self.hass, None, ENTITY_CLIMATE)
         self.hass.block_till_done()
         assert 'off' == state.attributes.get('aux_heat')
 
diff --git a/tests/components/demo/test_media_player.py b/tests/components/demo/test_media_player.py
index 808e3ee2102..fae4215f954 100644
--- a/tests/components/demo/test_media_player.py
+++ b/tests/components/demo/test_media_player.py
@@ -90,7 +90,8 @@ class TestDemoMediaPlayer(unittest.TestCase):
 
         assert False is state.attributes.get('is_volume_muted')
 
-        common.mute_volume(self.hass, None, entity_id)
+        with pytest.raises(vol.Invalid):
+            common.mute_volume(self.hass, None, entity_id)
         self.hass.block_till_done()
         state = self.hass.states.get(entity_id)
         assert False is state.attributes.get('is_volume_muted')
diff --git a/tests/components/demo/test_water_heater.py b/tests/components/demo/test_water_heater.py
index d8c9c71935b..e336e879f91 100644
--- a/tests/components/demo/test_water_heater.py
+++ b/tests/components/demo/test_water_heater.py
@@ -95,7 +95,8 @@ class TestDemowater_heater(unittest.TestCase):
         """Test setting the away mode without required attribute."""
         state = self.hass.states.get(ENTITY_WATER_HEATER)
         assert 'off' == state.attributes.get('away_mode')
-        common.set_away_mode(self.hass, None, ENTITY_WATER_HEATER)
+        with pytest.raises(vol.Invalid):
+            common.set_away_mode(self.hass, None, ENTITY_WATER_HEATER)
         self.hass.block_till_done()
         assert 'off' == state.attributes.get('away_mode')
 
diff --git a/tests/helpers/test_config_validation.py b/tests/helpers/test_config_validation.py
index 4b65904b8b2..6124699d88e 100644
--- a/tests/helpers/test_config_validation.py
+++ b/tests/helpers/test_config_validation.py
@@ -17,11 +17,14 @@ def test_boolean():
     """Test boolean validation."""
     schema = vol.Schema(cv.boolean)
 
-    for value in ('T', 'negative', 'lock'):
+    for value in (
+            None, 'T', 'negative', 'lock', 'tr  ue',
+            [], [1, 2], {'one': 'two'}, test_boolean):
         with pytest.raises(vol.MultipleInvalid):
             schema(value)
 
-    for value in ('true', 'On', '1', 'YES', 'enable', 1, True):
+    for value in ('true', 'On', '1', 'YES', '   true  ',
+                  'enable', 1, 50, True, 0.1):
         assert schema(value)
 
     for value in ('false', 'Off', '0', 'NO', 'disable', 0, False):