Don't skip all tests without DISPLAY set.

We used qapp in a session scoped fixture, which means testing without DISPLAY
skipped all tests.

tests/conftest.py

@@ -96,10 +96,11 @@ def pytest_runtest_setup(item):
         pytest.skip("Can only run when frozen!")
 
 
-@pytest.fixture(autouse=True, scope='session')
-def change_qapp_name(qapp):
+@pytest.fixture(scope='session')
+def qapp(qapp):
     """Change the name of the QApplication instance."""
     qapp.setApplicationName('qute_test')
+    return qapp
 
 
 class WinRegistryHelper:

tests/test_conftest.py

@@ -0,0 +1,30 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2015 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser 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 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser 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 qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Various meta-tests for conftest.py."""
+
+
+def test_qapp_name(qapp):
+    """Make sure the QApplication name is changed when we use qapp."""
+    assert qapp.applicationName() == 'qute_test'
+
+
+def test_foo(request):
+    """Make sure a test without qapp doesn't use qapp (via autouse)."""
+    assert 'qapp' not in request.fixturenames