Flask Testing: Test App Request?

Question

While doing the Miguel Grinberg's Flask Web Development, I got stuck while testing the gravatar code,

def test_gravatar(self):
    u = User(email='john@example.com', password='cat')
    with self.app.test_request_context('/'):
        gravatar = u.gravatar()
        gravatar_256 = u.gravatar(size=256)
        gravatar_pg = u.gravatar(rating='pg')
        gravatar_retro = u.gravatar(default='retro')
    with self.app.test_request_context('/', base_url='https://example.com'):
        gravatar_ssl = u.gravatar()
    self.assertTrue('http://www.gravatar.com/avatar/' +
                    'd4c74594d841139328695756648b6bd6'in gravatar)
    self.assertTrue('s=256' in gravatar_256)
    self.assertTrue('r=pg' in gravatar_pg)
    self.assertTrue('d=retro' in gravatar_retro)
    self.assertTrue('https://secure.gravatar.com/avatar/' +
                    'd4c74594d841139328695756648b6bd6' in gravatar_ssl)

What does app.test_request_context() do and how is it different from app_context()?

Why do we even need to call with self.app.test_request_context('/')? Also, what changes can we do to shift the call to app.test_request_context() in SetUp()?

score 4 · Answer 1 · edited Apr 09 '19 at 10:26

There's plenty of reading to do on the subject, so start with the documentation: app_context, test_request_context, and you can always double-check the code: app_context and test_request_context. In addition, here's an article discussion Flask's contexts.

That's a lot of links, so for a break-down:

We can see that app_context creates a new application context, while test_request_context creates a new request context. Application contexts are created in two situations: manually with app_context and when a request context is created, which, in turn, is created with test_request_context or at the beginning of the request.

So when a request comes into your application, a RequestContext is created. The creation of this object creates an application context.

Why test_request_context? You need that context to access the application when working outside of a context created by a request, like proxies that you probably recognize, like current_app, request, g, and session. Going down into the code, when you create a RequestContext with test_request_context instead of request_context, you're getting a EnvironBuilder object.

X.C. · Answer 2 · 2017-09-16T09:22:36.307

Check out tbicr 's answer here.

Specifically, this snippet of code

gravatar = u.gravatar()
gravatar_256 = u.gravatar(size=256)
gravatar_pg = u.gravatar(rating='pg')
gravatar_retro = u.gravatar(default='retro')

requires request context since it needs to access 'request' variable.

The definition of gravatar method in User Model needs 'request' variable.

def gravatar(self, size=100, default='identicon', rating='g'): 
        if request.is_secure: # here
            url = 'https://secure.gravatar.com/avatar' 
        else:  
            url = 'http://www.gravatar.com/avatar' 
        hash = self.avatar_hash or hashlib.md5(self.email.encode('utf-8')).hexdigest() 
        return '{url}/{hash}?s={size}&d={default}&r={rating}'.format(url=url, hash=hash, size=size, default=default, rating=rating)

Flask Testing: Test App Request?

2 Answers2