Add @with/out_apps TestCase decorators

Add decorators for adding and removing apps from INSTALLED_APPS in test
cases.

analytical/tests/test_tag_chartbeat.py

@@ -11,16 +11,18 @@ from django.template import Context
 
 from analytical.templatetags.chartbeat import ChartbeatTopNode, \
         ChartbeatBottomNode
-from analytical.tests.utils import TagTestCase, override_settings
+from analytical.tests.utils import TagTestCase, with_apps, without_apps
 from analytical.utils import AnalyticalException
 
-@override_settings(INSTALLED_APPS=[
-        a for a in settings.INSTALLED_APPS if a != 'django.contrib.sites'])
+
+@without_apps('django.contrib.sites')
 class ChartbeatTagTestCaseNoSites(TagTestCase):
     def test_rendering_setup_no_site(self):
         r = ChartbeatBottomNode().render(Context())
         self.assertTrue('var _sf_async_config={"uid": "12345"};' in r, r)
 
+
+@with_apps('django.contrib.sites')
 class ChartbeatTagTestCaseWithSites(TagTestCase):
     def test_rendering_setup_site(self):
         site = Site.objects.create(domain="test.com", name="test")
@@ -31,11 +33,6 @@ class ChartbeatTagTestCaseWithSites(TagTestCase):
             self.assertTrue(re.search(
                     'var _sf_async_config={.*"domain": "test.com".*};', r), r)
 
-# Ensure django.contrib.sites is in INSTALLED_APPS
-if "django.contrib.sites" not in settings.INSTALLED_APPS:
-    installed_apps = list(settings.INSTALLED_APPS)
-    installed_apps.append("django.contrib.sites")
-    ChartbeatTagTestCaseWithSites = override_settings(INSTALLED_APPS=installed_apps)(ChartbeatTagTestCaseWithSites)
 
 class ChartbeatTagTestCase(TagTestCase):
     """

analytical/tests/utils.py

@@ -13,6 +13,8 @@ from django.utils.functional import wraps
 
 class override_settings(object):
     """
+    Temporarily override Django settings.
+
     Acts as either a decorator, or a context manager.  If it's a decorator it
     takes a function and returns a wrapped function.  If it's a contextmanager
     it's used with the ``with`` statement.  In either event entering/exiting
@@ -46,6 +48,7 @@ class override_settings(object):
     def disable(self):
         settings._wrapped = self.wrapped
 
+
 def run_tests(labels=()):
     """
     Use the Django test runner to run the tests.
@@ -53,6 +56,25 @@ def run_tests(labels=()):
     django_run_tests(labels, verbosity=1, interactive=True)
 
 
+def with_apps(*apps):
+    """
+    Class decorator that makes sure the passed apps are present in
+    INSTALLED_APPS.
+    """
+    apps_set = set(settings.INSTALLED_APPS)
+    apps_set.update(apps)
+    return override_settings(INSTALLED_APPS=list(apps_set))
+
+
+def without_apps(*apps):
+    """
+    Class decorator that makes sure the passed apps are not present in
+    INSTALLED_APPS.
+    """
+    apps_list = [a for a in settings.INSTALLED_APPS if a not in apps]
+    return override_settings(INSTALLED_APPS=apps_list)
+
+
 class TestCase(DjangoTestCase):
     """
     Base test case for the django-analytical tests.