I would suggest you use `assert` here instead of `eq_` and `ok_`. I know it's perhaps silly nitpicking but `assert` signals assumptions, not hopes. 
The point with `assert` is that it's not the test. It's just something that can't go wrong. Also, an `assert` signals to the reader of the code that this is what needs to be true and assumed but it's also a way to explaining what is in the fixtures sometimes. 

I know it's nitpicking but in really pretty test code there's only one thing you want to test. If you're unsure about something working then write a dedicated test for that. For example::

```python
# WRONG
def test_has_permission(self):
    user = self._create_sample_user()
    ok_(not user.is_staff)
    ok_(not has_permission(user, 'some-permission'))
    user.is_staff = True
    user.save()
    ok_('some-permission' in KNOWN_PERMISSIONS)
    ok_(has_permission(user, 'some-permission'))
```


```python
# BETTER
def test_has_permission(self):
    user = self._create_sample_user()
    assert not user.is_staff, "check your fixture function"
    ok_(not has_permission(user, 'some-permission'))
    user.is_staff = True
    user.save()
    assert 'some-permission' in KNOWN_PERMISSIONS
    ok_(has_permission(user, 'some-permission'))
```
Does that make sense?