How to mock Session.request without losing auth?

Question

When testing Python software that uses the requests library, it is advised to mock requests.sessions.Session.request.

Unfortunately that doesn't seem to work very well when having to deal with HTTP Authentication, I feel like I am mocking a too high abstraction layer in requests. How can I intercept/mock requests such that I don't have to deal with authentication myself (and just get the appropriate headers)?

Answer 1

Don't mock the Session, use a Transport Adapter. =)

The Session object does substantial processing on the request, and patching it at that level won't get you the request.

Instead, write a Transport Adapter whose send() method stores off the PreparedRequest object.

For examples, see the official docs and an article I wrote. However, you'll want something like this:

from requests.adapters import HTTPAdapter


class TestAdapter(HTTPAdapter):
    """
    A Transport Adapter that stores all requests sent, and provides pre-canned responses.
    """
    def __init__(self, responses):
        self.responses = responses
        self.requests = requests

    def send(self, request, *args, **kwargs):
        self.requests.append(request)
        return self.responses.pop(0)

To get this to work responses will need to be a list of urllib3.Response objects or something similar that Requests can work with. TestAdapter.requests will be a list of requests.PreparedRequest objects.

If you don't want to do all this work, you can try something like betamax.