Checking Permissions in django TestCase

I am trying to test my create_user view in a django1.8 app. I have the following in a TestCase:

    new_user = User.objects.get(username='test')
    basic_user_group = Group.objects.get(name='basic_users')
    self.assertIn(basic_user_group, new_user.groups.all()) # passes

    print new_user.groups.all()
    # [<Group: basic_users>]

    print new_user.groups.first().permissions.all()
    # [<Permission: foo_app | 'add_bar'>]

    print new_user.get_all_permissions()
    # set([]) # Why?

    self.assertTrue(new_user.has_perm('foo_app.add_bar')) # fails

When I use the actual app to create a user then open up the shell to check has_perm('foo_app.add_bar'), it's True. What's going wrong in the test?

I am using django-guardian for object permissions. My settings.AUTHENTICATION_BACKENDS is:

(
    'guardian.backends.ObjectPermissionBackend',
    'django.contrib.auth.backends.ModelBackend',
)