Return Iterable With Mock Python

Question

I'm trying to use Mock, to simulate a function in python. Here is my code:

    resp, content = request(...) 

The request() function needs to return two values. Here's what I tried:

    with patch("syncdatetime.py") as sync_mock:         sync_mock.request.return_value = [obj, ''] 

But when I run the test, I get the error "Mock object is not iterable." The request function returns an object of type Mock instead of a list. How can I patch the request function so that it returns a list?

Answer 1

I suspect that your problem is that you are not using the instance of mock that you think you are. By default an instance of Mock returns a Mock when called.

>>> m = mock.Mock() >>> type(m()) <class 'mock.mock.Mock'>     

It looks like your call to request is returning a Mock because the return_value has not been initialized which means that resp, content = request() is trying to unpack a Mock object.

>>> m = mock.Mock() >>> (a, b) = m() Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: 'Mock' object is not iterable 

You shouldn't need to use side_effect to return a list. Assigning return_value should work.

>>> m = mock.Mock() >>> m.return_value = ['a', 'b'] >>> (a, b) = m() >>> a 'a' >>> b 'b' 

Answer 2

Note of disclosure, I'm new to mock so I'm not an expert, however, I have just suffered the same problem and found that setting the side_effect attribute to a function that returns an array fixes things

From your example code, change:

with patch("syncdatetime.py") as sync_mock:     sync_mock.request.return_value = [obj, ''] 

to

with patch("syncdatetime.py") as sync_mock:     sync_mock.request.side_effect = function_returning_list 

and define

def function_returning_list(arg_list_of_choice):     #anything you want to do goes here     #then     return your_list