unit testing - Why don't my Django unittests know that MessageMiddleware is installed?

Question

I'm working on a Django project and am writing unittests for it. However, in a test, when I try and log a user in, I get this error:

MessageFailure: You cannot add messages without installing django.contrib.messages.middleware.MessageMiddleware

Logging in on the actual site works fine -- and a login message is displayed using the MessageMiddleware.

In my tests, if I do this:

from django.conf import settings
print settings.MIDDLEWARE_CLASSES

Then it outputs this:

('django.middleware.cache.UpdateCacheMiddleware',
'django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',

'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware',
'django.middleware.cache.FetchFromCacheMiddleware',
'debug_toolbar.middleware.DebugToolbarMiddleware')

Which appears to show the MessageMiddleware is installed when tests are run.

Is there an obvious step I'm missing?

UPDATE

After suggestions below, it does look like it's a settings thing.

I currently have settings/__init__.py like this:

try:
    from settings.development import *
except ImportError:
    pass

and settings/defaults.py containing most of the standard settings (including MIDDLEWARE_CLASSES). And then settings.development.py overrides some of those defaults like this:

from defaults import *

DEBUG = True
# etc

It looks like my dev site itself works fine, using the development settings. But although the tests seem to load the settings OK (both defaults and development) settings.DEBUG is set to False. I don't know why, or whether that's the cause of the problem.

Answer 1

Django 1.4 has a expected behavior when you create the request with RequestFactory that can trigger this error.

To resolve this issue, create your request with RequestFactory and do this:

from django.contrib.messages.storage.fallback import FallbackStorage
setattr(request, 'session', 'session')
messages = FallbackStorage(request)
setattr(request, '_messages', messages)

Works for me!