[gnome-control-center/wip/benzea/ci-network: 14/17] tests: Add dbusmock helper starting X server and system/session busses

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 8c9be792f25ce4d636e55d0872944936e45517a4
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Apr 6 16:59:37 2018 +0200

    tests: Add dbusmock helper starting X server and system/session busses
    
    This helper has been submitted for inclusion in dbusmock. If it cannot
    live there in some form, then we should try to find a home in the GNOME
    project for it.

 tests/shared/x11session.py | 101 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
---
diff --git a/tests/shared/x11session.py b/tests/shared/x11session.py
new file mode 100644
index 000000000..87e964943
--- /dev/null
+++ b/tests/shared/x11session.py
@@ -0,0 +1,101 @@
+# Copyright © 2018 Red Hat, Inc
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <http://www.gnu.org/licenses/>.
+#
+# Authors: Benjamin Berg <bberg redhat com>
+
+import os
+import sys
+import subprocess
+from dbusmock import DBusTestCase
+
+# Intended to be shared across projects, submitted for inclusion into
+# dbusmock but might need to live elsewhere
+# The pull request contains python 2 compatibility code.
+#  https://github.com/martinpitt/python-dbusmock/pull/44
+
+class X11SessionTestCase(DBusTestCase):
+    #: The display the X server is running on
+    X_display = -1
+    #: The X server to start
+    Xserver = 'Xvfb'
+    #: Further parameters for the X server
+    Xserver_args = ['-screen', '0', '1280x1024x24', '+extension', 'GLX']
+    #: Where to redirect the X stdout and stderr to. Set to None for debugging
+    #: purposes if the X server is failing for some reason.
+    Xserver_output = subprocess.DEVNULL
+
+    @classmethod
+    def setUpClass(klass):
+        klass.start_xorg()
+        klass.start_system_bus()
+        klass.start_session_bus()
+
+    @classmethod
+    def start_xorg(klass):
+        r, w = os.pipe()
+
+        # Xvfb seems to randomly crash in some workloads if "-noreset" is not given.
+        #  https://bugzilla.redhat.com/show_bug.cgi?id=1565847
+        klass.xorg = subprocess.Popen([klass.Xserver, '-displayfd', "%d" % w, '-noreset'] + 
klass.Xserver_args,
+                                      pass_fds=(w,),
+                                      stdout=klass.Xserver_output,
+                                      stderr=subprocess.STDOUT)
+        os.close(w)
+
+        # The X server will write "%d\n", we need to make sure to read the "\n".
+        # If the server dies we get zero bytes reads as EOF is reached.
+        display = b''
+        while True:
+            tmp = os.read(r, 1024)
+            display += tmp
+
+            # Break out if the read was empty or the line feed was read
+            if not tmp or tmp[-1] == b'\n':
+                break
+
+        os.close(r)
+
+        try:
+            display = int(display.strip())
+        except ValueError:
+            # This should never happen, the X server didn't return a proper integer.
+            # Most likely it died for some odd reason.
+            # Note: Set Xserver_output to None to debug Xvfb startup issues.
+            klass.stop_xorg()
+            raise AssertionError('X server reported back no or an invalid display number (%s)' % (display))
+
+        klass.X_display = display
+        # Export information into our environment for tests to use
+        os.environ['DISPLAY'] = ":%d" % klass.X_display
+        os.environ['WAYLAND'] = ''
+
+        # Server should still be up and running at this point
+        assert klass.xorg.poll() is None
+
+        return klass.X_display
+
+    @classmethod
+    def stop_xorg(klass):
+        if hasattr(klass, 'xorg'):
+            klass.X_display = -1
+            klass.xorg.terminate()
+            klass.xorg.wait()
+            del klass.xorg
+
+    @classmethod
+    def tearDownClass(klass):
+        DBusTestCase.tearDownClass()
+
+        klass.stop_xorg()