How to check template context using Pyramid + webtest

Question

I'm starting writing tests for my Pyramid views (using webtest), and coming from a Django background I'm having an hard time trying to understand how to test that certain variables have been passed to the template. For example let's consider this view:

@view_config(route_name='login_or_signup', renderer='login_or_signup.html')
def login_or_sign_up(request):
    if request.method == 'POST':
        try:
            do_business_logic()
            return HTTPFound(location=next)
        except Invalid as e:
            request.response.status_code = 400
            return dict(form_errors=e.asdict())
    return {}

How can I write a test that proves that if the form is incorrect, a form_errors dictionary is passed to the template? In Django I would use the context attribute, but in Pyramid/webtest I can't find nothing similar... It seems that template's data is not accessible via the response object. The only thing I found in order to access this data is via event listeners:

@subscriber(BeforeRender)
def print_template_context(event):
    for k, v in event.rendering_val.items():
        print(k, v)

But I think that is not feasible to use such approach, since:

it's a global listener
it has no access to the response object

So... I tried to extend the base Response class (in order to attach extra fields to it):

class TemplateResponse(Response):
    def __init__(self, template, template_context=None, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.template = template
        self.template_context = template_context or {}
        self.text = render(self.template, self.template_context, self.request)

and change the original view to:

   @view_config(route_name='login_or_signup')
    def login_or_sign_up(request):
        if request.method == 'POST':
            try:
                do_buisness_logic()
                return HTTPFound(location=next)
            except Invalid as e:
                return TemplateResponse(
                    'login_or_signup.html', 
                    dict(form_errors=e.asdict()), 
                    status=400
            )
        return TemplateResponse('login_or_signup.html')

But it's helpless, since webtest returns its own TestResponse object instead of my TemplateResponse... so how can I test data in templates?

score 0 · Answer 1 · answered Jan 26 '16 at 10:12

Despite I'm not totally satisfied, I currently solved using both webtest and default Pyramid test utils:

template_request = DummyRequest(path='/login-signup', post=data)
template_context = LoginSignupView(template_request).post()
response = self.app.post('/login-signup', data, status=HTTPBadRequest.code)
self.assertEqual(response.status_code, HTTPBadRequest.code)
self.assertIsInstance(template_context['form_errors'], dict)

the DummyRequest is passed directly to the View, which simply returns a dictionary containing template variables. Instead the actual "navigation" is delegated to the TestApp instance which is able to get back the actual html response that has been rendered.

How to check template context using Pyramid + webtest

1 Answers1