[gnome-settings-daemon/wip/benzea/backlight: 10/10] power: Add test to verify DBus behaviour without a backlight

[Benjamin Berg <bberg src gnome org>]

commit 08c6f8a7db0eed52940fade9f2a6f38246b0346e
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Sep 21 17:14:03 2018 +0200

    power: Add test to verify DBus behaviour without a backlight
    
    In the case that we have no backlight (for the screen) the DBus
    interface will partially work. Querying the brightness will result in a
    static value of -1. Trying to set the brightness in any way will instead
    result in a DBus error.

 plugins/power/test.py | 40 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 37 insertions(+), 3 deletions(-)
---
diff --git a/plugins/power/test.py b/plugins/power/test.py
index 8ef46433..c789940c 100755
--- a/plugins/power/test.py
+++ b/plugins/power/test.py
@@ -54,8 +54,8 @@ class PowerPluginTest(gsdtestcase.GSDTestCase):
         os.environ['UMOCKDEV_DIR'] = self.testbed.get_root_dir()
 
         # Create a mock backlight device
-        # Note that this function creates a different backlight device based on
-        # the name of the test.
+        # Note that this function creates a different or even no backlight
+        # device based on the name of the test.
         self.add_backlight()
 
         # start mock upowerd
@@ -214,7 +214,9 @@ class PowerPluginTest(gsdtestcase.GSDTestCase):
     def backlight_defaults(self):
         # Hack to modify the brightness defaults before starting gsd-power.
         # The alternative would be to create two separate test files.
-        if 'legacy_brightness' in self.id():
+        if 'no_backlight' in self.id():
+            return None, None
+        elif 'legacy_brightness' in self.id():
             return 15, 15
         else:
             return 100, 50
@@ -222,6 +224,10 @@ class PowerPluginTest(gsdtestcase.GSDTestCase):
     def add_backlight(self, _type="raw"):
         max_brightness, brightness = self.backlight_defaults()
 
+        if max_brightness is None:
+            self.backlight = None
+            return
+
         # Undo mangling done in GSD
         if max_brightness >= 99:
             max_brightness += 1
@@ -1186,5 +1192,33 @@ class PowerPluginTest(gsdtestcase.GSDTestCase):
         time.sleep(0.2)
         self.assertEqual(self.get_brightness(), 15)
 
+    def test_no_backlight(self):
+        '''Check that backlight brightness DBus api without a backlight'''
+
+        obj_gsd_power = self.session_bus_con.get_object(
+            'org.gnome.SettingsDaemon.Power', '/org/gnome/SettingsDaemon/Power')
+        obj_gsd_power_props = dbus.Interface(obj_gsd_power, dbus.PROPERTIES_IFACE)
+        obj_gsd_power_screen = dbus.Interface(obj_gsd_power, 'org.gnome.SettingsDaemon.Power.Screen')
+
+        # We expect -1 to be returned
+        brightness = obj_gsd_power_props.Get('org.gnome.SettingsDaemon.Power.Screen', 'Brightness')
+        self.assertEqual(brightness, -1)
+
+        # Trying to set the brightness
+        with self.assertRaises(dbus.DBusException) as exc:
+            obj_gsd_power_props.Set('org.gnome.SettingsDaemon.Power.Screen', 'Brightness', 1)
+
+        self.assertEqual(exc.exception.get_dbus_message(), 'No usable backlight could be found!')
+
+        with self.assertRaises(dbus.DBusException) as exc:
+            obj_gsd_power_screen.StepUp()
+
+        self.assertEqual(exc.exception.get_dbus_message(), 'No usable backlight could be found!')
+
+        with self.assertRaises(dbus.DBusException) as exc:
+            obj_gsd_power_screen.StepDown()
+
+        self.assertEqual(exc.exception.get_dbus_message(), 'No usable backlight could be found!')
+
 # avoid writing to stderr
 unittest.main(testRunner=unittest.TextTestRunner(stream=sys.stdout, verbosity=2))