How to unit test the innards of a Django view function

14^th of November 2008

Seconds ago I got this running and haven't yet fully understood what I've just done but the results are exactly what I need and this is going to be great.

Basically, in Django you have views like this:

def _render(template, data, request):
    return render_to_response(template, data,
              context_instance=RequestContext(request))

@login_required
def club_page(request, year):
    variable1 = year / 4
    variable2 = variable1 * 2
    return _render("foo.html", locals(), request)

Now in my unit tests I don't want to have to call the view function and then have to dissect the resulting HTML just to figure out if the view function prepared the correct variables. So, here's my solution to this problem:

In 'test_views.py':

from my_app.views import club_page

# mutable globals for capturing the traffic through _render
snatched_templates = []
snatched_data = []
snatched_requests = []
def _fake_render(template, data, request):
    snatched_templates.append(template)
    snatched_data.append(data)
    snatched_requests.append(request)
    return render_to_response(template, data,
              context_instance=RequestContext(request))

class FakeRequest(object):
    def __init__(self, get=None, post=None, user=None):
        self.get = get
        self.post = post
        self.user = user

    def GET(self):
        return self.get

    def POST(self):
        return self.post

class ViewsTestCase(unittest.TestCase):
    def test_club_page(self):

         # add a test user
        from django.contrib.auth.models import User
        user = User.objects.create_user(username='t', password='t',
                 email='t@t.com')

        # prepare a request
        request = FakeRequest(user=staff)

        from my_app import views
        views._render = _fake_render

        response = club_day_page(request, 'fool', 2004)
        assert response.count('</html>')
        assert snatched_data[-1]['variable2'] == 102

This isn't really something a novice test driven Django developer can just copy since I've scribbled this code as pseudo code. My code for my app is a bit more complicated than this but the principle is the same.

So, tell me Django gurus, have I reinvented the wheel here or are other people finding this useful?

UPDATE

There is a more convenient way but it's quite arcane. After a client request has been made the response has an attribute context that you can use. E.g.:

response = client.get('/club/Test_club2/attendance-report/')
context_data = response.context[-1].dicts[0]
pprint(context_data)

This approach, unlike my hack mentioned first, however requires that you have a publishable URL first.

Thanks Stephen!

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