python unittest mock a nested function

Question

i have a function x in main.applications.handlers package

from main.config import get_db

def x(company_name):
        db = get_db('my_db')
        apps = []
        for x in company_db.applications.find():
            print(x)
            apps.append(x)
        return apps

now i want to write unittest for this method .

from unittest.mock import Mock,patch, MagicMock

@mock.patch('main.applications.handlers.get_db')
def test_show_applications_handler(self, mocked_db):
    mocked_db.applications.find  = MagicMock(return_value=[1,2,3])
    apps = x('test_company') # apps should have [1,2,3] but its []
    print(apps)

but company_db.applications.find() inside main.applications.handlers is not returning anything .it should return [1,2,3] what could be wrong with this code?

what do you get if you replace the x in apps = x('test_company') with find? — Nick
– Nick, Commented Dec 19, 2018 at 11:33
@Nick i get <MagicMock name='get_db().applications.find()' id='140565332675720'> when i do print (company_db.applications.find()) inside x — anekix
– anekix, Commented Dec 19, 2018 at 11:37
i also tried this mocked_db.return_value.applications.return_value.find.return_value = [1,2,3] but same result — anekix
– anekix, Commented Dec 19, 2018 at 11:39
Is company_db a typo? I can't see where that is defined. Presumably it should be db? — Will Keeling
– Will Keeling, Commented Dec 19, 2018 at 17:44

Will Keeling · Accepted Answer · 2018-12-19 17:56:22Z

2

Assuming that company_db is a typo and should be db, then to mock the return value of find(), you would do:

mocked_db.return_value.applications.find = MagicMock(return_value=[1,2,3])

mocked_db requires a return_value because get_db is called with the database name.

You could also drop the MagicMock and set the return_value of find directly:

mocked_db.return_value.applications.find.return_value = [1, 2, 3]

answered Dec 19, 2018 at 17:56

Will Keeling

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1 Comment

anekix Over a year ago

@WillKeeping it worked when i used mocked_db().return_value.applications.find = MagicMock(return_value=[1,2,3]) but not with mocked_db.return_value.applications.find = MagicMock(return_value=[1,2,3])

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