Development with Python

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Creating a User if Necessary
Next we should check that, if our authenticate function has a valid assertion from
Persona, but we don’t have a user record for that person in our database, we should
create one. Here’s the test for that:
accounts/tests/test_authentication.py (ch16l027).
def test_creates_new_user_if_necessary_for_valid_assertion(self, mock_post):
mock_post.return_value . json.return_value = {'status': 'okay', 'email': }
found_user = self .backend.authenticate ('an assertion')
new_user = User .objects.get(email = )
self.assertEqual(found_user, new_user)
That fails in our application code when we try find an existing user with that email:
return User.objects.get(email=response.json()['email'])
django.contrib.auth.models.DoesNotExist: User matching query does not exist.
So we add a try/except, returning an “empty” user at first:
accounts/authentication.py (ch16l028).
if response.ok and response.json()['status'] == 'okay':
try:
return User.objects.get (email =response.json()['email'])
except User.DoesNotExist:
return User.objects.create ()
And that fails, but this time it fails when the test tries to find the new user by email:
new_user = User.objects.get(email= )
django.contrib.auth.models.DoesNotExist: User matching query does not exist.
And so we fix it by assigning the correct email addresss:
accounts/authentication.py (ch16l029).
if response.ok and response.json()['status'] == 'okay':
email = response.json()['email']
try:
return User.objects.get (email =email)
except User.DoesNotExist:
return User.objects.create (email= email)
That gets us to passing tests:
$ python3 manage.py test accounts
[...]
Ran 9 tests in 0.019s
OK
The get_user Method
The next thing we have to build is a get_user method for our authentication backend.
This method’s job is to retrieve a user based on their email address, or to return None if
it can’t find one. (That last wasn’t well documented at the time of writing, but that is the
interface we have to comply with. See for details.)
De-spiking Our Custom Authentication Backend: Mocking Out an Internet Request | 291