Testing Django Middlewares

October 31, 2018

I have reached the dilemma that unit testing my middlewares in django doesn’t seem enough so I came up with a different approach.

What I want is to test the same request object as my django views receives it.

This is my ugly solution, please forgive me.

Step 1: Create an Ugly Test Url

if settings.DEBUG:
    urlpatterns += [
        url(r'^test/', test, name='test'),
    ]

Setp 2: Create an even uglier Test View

You must return an HttpResponse object with a req attribute containing the actual request. Keep in mind that the attribute request already exists and that’s why I am using req

def test(request):
    response = HttpResponse('Testing')
    response.req = request
    return response

Step 3: Test your middleware

Call the endpoint /test/ with the django client class and assert the response.req object. For example …

@pytest.mark.django_db
def test_company(client, default_user, company_user, administrator, salesman, site_settings):
    # testing anonymous
    site_settings.price_visibility = SiteSettings.ANONYMOUS
    site_settings.save()
    response = client.get('/test/', follow=True)
    assert response.req.hide_prices is False

    # testing logged user
    site_settings.price_visibility = SiteSettings.LOGGED
    site_settings.save()
    response = client.get('/test/', follow=True)
    assert response.req.hide_prices is True

    client.login(username=default_user.email, password='password')
    response = client.get('/test/', follow=True)
    assert response.req.hide_prices is False
    client.logout()

    # testing user with company
    site_settings.price_visibility = SiteSettings.WITH_CLIENT
    site_settings.save()
    response = client.get('/test/', follow=True)
    
    assert response.req.hide_prices is True
    client.login(username=default_user.email, password='password')
    response = client.get('/test/', follow=True)
    
    assert response.req.hide_prices is True
    client.logout()
    client.login(username=company_user.email, password='password')
    response = client.get('/test/', follow=True)
    assert response.req.hide_prices is False
    client.logout()

    ...

The problem

For example, at work I have to write a middleware with something like this

class HidePricesMiddleware(object):
    def process_request(self, request):
        request_visibility = SiteSettings.ADMINISTRATOR
        if not request.user.is_authenticated():
            request_visibility = SiteSettings.ANONYMOUS
        elif request.user.is_staff:
            request_visibility = SiteSettings.ADMINISTRATOR
        elif not request.user.company:
            request_visibility = SiteSettings.LOGGED
        elif not request.user.company.show_prices:
            request_visibility = SiteSettings.WITH_CLIENT
        else:
            request_visibility = SiteSettings.APPROVED

        request.hide_prices = request_visibility < request.site_settings.price_visibility

When I try to test this middleware by unit testing it I started mocking all posible cases and after some time it felt very uncomfortable (IMHO) because I end up writing the test to match the code. In the previous example testing was way more natural for me.

Hope it helps.