Tests with xvfb on travis, requiring herbstluftwm

A window manager is required to better test qt application under xvfb.

.travis.yml

@@ -1,4 +1,4 @@
-sudo: false
+sudo: true
 language: python
 dist: trusty
 python: 3.6
@@ -10,7 +10,8 @@ cache:
 install:
   - pip install PyQt5
   - pip install -r test-requirements.txt
+  - sudo apt-get --yes install xvfb herbstluftwm
 
 script:
   - flake8 webmacs setup.py
-  - pytest --ignore tests/integration/ tests
+  - pytest tests

test-requirements.txt

@@ -2,4 +2,5 @@
 pytest
 pytest-qt
 pytest-mock
+pytest-xvfb
 flake8

tests/integration/conftest.py

@@ -1,6 +1,7 @@
 import pytest
 import os
 import time
+import subprocess
 
 from PyQt5.QtTest import QTest
 from PyQt5.QtWebEngineWidgets import QWebEngineView
@@ -37,8 +38,30 @@ def iter_widgets_for_events(w):
         yield w
 
 
+@pytest.fixture(scope="session")
+def wm(xvfb):
+    if xvfb is None:
+        yield None
+    else:
+        if not any(
+                os.access(os.path.join(path, 'herbstluftwm'), os.X_OK)
+                for path in os.environ["PATH"].split(os.pathsep)
+        ):
+            raise RuntimeError("herbstluftwm is not installed, can not run"
+                               " graphical tests.")
+        env = dict(os.environ)
+        env["DISPLAY"] = str(":%s" % xvfb.display)
+        proc = subprocess.Popen(
+            ["herbstluftwm"], env=env
+        )
+        time.sleep(2)  # wait for the wm to be active
+        yield proc
+        proc.kill()
+        proc.wait()
+
+
 @pytest.fixture(scope='session')
-def qapp(qapp_args):
+def qapp(wm, qapp_args):
     _app_requires()
     global _app
     # TODO FIXME use another path for tests