Demonstrate "black pipe" testing a MongoDB application using MockupDB: http://mockupdb.readthedocs.org/

flask-app-test-demo.py

import logging
import unittest

from flask import Flask, make_response
from pymongo import MongoClient
from pymongo.errors import ConnectionFailure
from mockupdb import go, MockupDB, Command


logging.basicConfig()


def make_app(mongodb_uri):
    app = Flask("my app")
    db = MongoClient(mongodb_uri)

    @app.route("/pages/<page_name>")
    def page(page_name):
        try:
            doc = db.content.pages.find_one({'name': page_name})
        except ConnectionFailure:
            return make_response('Closed for renovations')
        return make_response(doc['contents'])

    return app


class MockupDBFlaskTest(unittest.TestCase):
    def setUp(self):
        self.server = MockupDB(auto_ismaster=True, verbose=True)
        self.server.run()
        self.app = make_app(self.server.uri).test_client()

    def tearDown(self):
        self.server.stop()

    def test(self):
        future = go(self.app.get, "/pages/my_page_name")
        request = self.server.receives(
            Command('find', 'pages', filter={'name': 'my_page_name'}))
        request.ok(cursor={'id': 0, 'firstBatch': [{'contents': 'foo'}]})
        http_response = future()
        self.assertEqual("foo",
                         http_response.get_data(as_text=True))

    def test_hangup(self):
        future = go(self.app.get, "/pages/my_page_name")
        request = self.server.receives(
            Command('find', 'pages', filter={'name': 'my_page_name'}))
        request.hangup()
        http_response = future()
        self.assertIn("renovations",
                      http_response.get_data(as_text=True))


if __name__ == '__main__':
    unittest.main()

Change gist filename extension so Github will highlight the Python code

Done, and updated for MongoDB 3.2's new "find" command protocol.