Sessions are empty when testing

This doc expresses that we can access session without any extra context manager.

However the following code does not return any session key (session is empty):

from flask import Flask


import pytest
from flask import session


myapp = Flask('testing')
myapp.secret_key = 'secret'
myapp.debug = True

@myapp.route('/')
def home():
    return session['message']


@pytest.fixture
def app():
    return myapp


def test_home(client):
    session['message'] = 'something'
    response = client.get('/')
    assert response.data == 'something'

Any hint on what we’re missing here?

Thanks 😃

[russmac]

Was also having this issue until I moved my yield client outside of the with client.session_transaction() as session: enumeration. You can debug by printing the session object, Which shows the secure cookie contents.

Wont work:

def client():
    with app.test_client() as client:
        with client.session_transaction() as session:
            session['Authorization'] = 'redacted'
            print(session) # will be empty SecureCookieSession
            yield client

Works:

def client():
    with app.test_client() as client:
        with client.session_transaction() as session:
            session['Authorization'] = 'redacted'
        print(session) # will be populated SecureCookieSession
        yield client

[northernSage]

Thanks @vinyll for taking the time to open the issue and all others for providing examples and a working solution. I feel like the issue could use a bit more info on why the described problem is happening.

While pytest-flask pushes a test request context for you at the beginning of the test session as stated in the docs

During test execution a request context will be automatically pushed for you, so context-bound methods can be conveniently called (e.g. url_for, session).

pytest-flask does not prevent flask from creating and pushing new request context objects onto the request context stack upon request handling. What this means and its consequences can be seen with help of the code snippet bellow:

def _context_info(scope, session):
    """shows current session and request context
       objects ids for debugging purposes"""
    print(scope, id(session._get_current_object()),
        " - session[message]: ",
        session.get("message", "not-found"),
        " - _request_ctx_stack top: ", 
        id(_request_ctx_stack.top))

def test_client_session(client, live_server):
    # adds a simple view that writes to session object
    @live_server.app.route('/home')
    def home():
        session["message"] = "BACON"
        _context_info("session id inside view: ", session)
        return "session updated"

    session["message"] = "EGGS"

    # checks context state before and after request
    _context_info("session id before request: ", session)
    response = client.get(url_for("home"))
    _context_info("session id after request: ", session)

    # pops top request object off stack
    print("poping top request context from stack...")
    _request_ctx_stack.pop()

    # check what is on top of stack
    _context_info("session id after popping request: ", session)

    assert False

Output:

...
----------------------------- Captured stdout call -----------------------------
session id before request:         139747393971024  - session[message]:   EGGS  - _request_ctx_stack top:  139747394620304
session id inside view:            139747393972272  - session[message]:  BACON  - _request_ctx_stack top:  139747394052432
session id after request:          139747393972272  - session[message]:  BACON  - _request_ctx_stack top:  139747394052432
popping top request context from stack...
session id after popping request:  139747393971024  - session[message]:   EGGS  - _request_ctx_stack top:  139747394620304

From this we can see that flask is pushing a new request context into the stack, shadowing the session object of the test request context pushed by pytest-flask and this seems to be the reason for the problem. The solution provided by @russmac is the official flask way of getting around this problem. A secondary possible solution would be using a view function (similar to my example above) to write to the session object and then access it using session["yourkey"] within your test since the session object will still be reachable:

def test_session(client, live_server):
    
    # temporary view just to alter session
    @live_server.app.route('/setsession')
    def set_session():
        session["message"] = "EGGS"
        return session["message"]
    
    response = client.get(url_for("set_session"))

    assert response.status == "200 OK"
    assert session["message"] == "EGGS"