How does one mock.patch a function inside a Flask Blueprint?

Question

I'm trying to use the unittest.mock library to patch a function inside a Flask Blueprint. Specifically, I'm trying to patch the os module inside the blueprint. Simplified code (cannot provide all/actual code):

test_route.py (the test I am trying to run)

import unittest
from unittest import mock

from server.index import create_app as Server

class TestRoute(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls.server = Server()
        cls.server.config['TESTING'] = True
        cls.client = cls.server.test_client()
        #
        # more code...
        #
    @mock.patch('server.routes.blueprint.os')
    def test_route(self, mockOS):
        mockOS.listdir.return_value = ['/mockedvalue']
        res = client.post('/some/url')
        #
        # more code...
        #

server/index.py (the module to create the Flask server)

from flask import Flask
from routes.blueprint import bp

def create_app():
    app = Flask(__name__)
    app.register_blueprint(bp)
    #
    # more code...
    #

server/routes/blueprint.py (the Blueprint logic used by the Flask server)

import os
from flask import Flask, Blueprint

bp = Blueprint('bp', __name__)

@bp.route('/some/url')
def run():
    #
    # code...
    #

    dirs = os.listdir('/some/path')    

    #
    # more code...
    #

When I run this, os.listdir() is not getting patched. I get the actual contents of '/some/path' when what I really want is the mocked value:

    Actual   : ['/something1', '/some/other/thing', ...]
    Expected : ['/mockedvalue']

I've read https://docs.python.org/3/library/unittest.mock.html#where-to-patch , but maybe I am still making a mistake. It seems appropriate to patch at the blueprint module, but if this is incorrect, any guidance or corrections would be appreciated.

Did you find a solution to this? – Geek Guy Aug 16 '22 at 11:18 — Geek Guy, Aug 16 '22 at 11:18

score 0 · Answer 1 · answered Feb 19 '20 at 07:52

what is happening if you set

    @mock.patch('server.routes.blueprint.os')
    def test_route(self, mockOS):
        with Server.app.app_context():        
            mockOS.listdir.return_value = ['/mockedvalue']
            res = client.post('/some/url')

How does one mock.patch a function inside a Flask Blueprint?

1 Answers1