From d076251b189c0a11f2bd528fdfdd0fb3d5dc8f5d Mon Sep 17 00:00:00 2001
From: Harvtronix <webmaster@harvtronix.com>
Date: Thu, 13 Sep 2018 10:38:07 -0400
Subject: [PATCH] Changing z-wave brightness calculation to respect 0x01 and
 0x02 byte values (#16420)

* Changing z-wave brightness calculation to respect 0x01 and 0x02 byte
values

* adding additional line breaks to satisfy houndci

* - Update comment style for linter
- Add additional unit test to increase code coverage

* Update zwave.py
---
 homeassistant/components/light/zwave.py | 12 +++++++++++-
 tests/components/light/test_zwave.py    | 20 ++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/homeassistant/components/light/zwave.py b/homeassistant/components/light/zwave.py
index 55feef496f8..1e768eb127a 100644
--- a/homeassistant/components/light/zwave.py
+++ b/homeassistant/components/light/zwave.py
@@ -63,6 +63,16 @@ def brightness_state(value):
     return 0, STATE_OFF
 
 
+def byte_to_zwave_brightness(value):
+    """Convert brightness in 0-255 scale to 0-99 scale.
+
+    `value` -- (int) Brightness byte value from 0-255.
+    """
+    if value > 0:
+        return max(1, int((value / 255) * 99))
+    return 0
+
+
 def ct_to_hs(temp):
     """Convert color temperature (mireds) to hs."""
     colorlist = list(
@@ -187,7 +197,7 @@ class ZwaveDimmer(zwave.ZWaveDeviceEntity, Light):
         # brightness. Level 255 means to set it to previous value.
         if ATTR_BRIGHTNESS in kwargs:
             self._brightness = kwargs[ATTR_BRIGHTNESS]
-            brightness = int((self._brightness / 255) * 99)
+            brightness = byte_to_zwave_brightness(self._brightness)
         else:
             brightness = 255
 
diff --git a/tests/components/light/test_zwave.py b/tests/components/light/test_zwave.py
index 62bcf834b98..5805c8eb2fb 100644
--- a/tests/components/light/test_zwave.py
+++ b/tests/components/light/test_zwave.py
@@ -105,6 +105,26 @@ def test_dimmer_turn_on(mock_openzwave):
         assert entity_id == device.entity_id
 
 
+def test_dimmer_min_brightness(mock_openzwave):
+    """Test turning on a dimmable Z-Wave light to its minimum brightness."""
+    node = MockNode()
+    value = MockValue(data=0, node=node)
+    values = MockLightValues(primary=value)
+    device = zwave.get_device(node=node, values=values, node_config={})
+
+    assert not device.is_on
+
+    device.turn_on(**{ATTR_BRIGHTNESS: 1})
+
+    assert device.is_on
+    assert device.brightness == 1
+
+    device.turn_on(**{ATTR_BRIGHTNESS: 0})
+
+    assert device.is_on
+    assert device.brightness == 0
+
+
 def test_dimmer_transitions(mock_openzwave):
     """Test dimming transition on a dimmable Z-Wave light."""
     node = MockNode()