'Tests apps.is_installed().'

@override_settings(INSTALLED_APPS=SOME_INSTALLED_APPS)
def test_is_installed(self):

    self.assertTrue(apps.is_installed('django.contrib.admin'))
    self.assertTrue(apps.is_installed('django.contrib.auth'))
    self.assertTrue(apps.is_installed('django.contrib.staticfiles'))
    self.assertFalse(apps.is_installed('django.contrib.admindocs'))
