How to taunt generators with mock.patch

Question

I looked at the page https://docs.python.org/3/library/unittest.mock-examples.html and I see that they gave an example of how to mock generators

I have code where I call a generator to give me a set of values ​​that I save as a dictionary. I want to make fun of the calls of this generator in my unit test.

I wrote the following code and it does not work.

Where am I mistaken?

In [7]: items = [(1,'a'),(2,'a'),(3,'a')] In [18]: def f(): print "here" for i in [1,2,3]: yield i,'a' In [8]: def call_f(): ...: my_dict = dict(f()) ...: print my_dict[1] ...: In [9]: call_f() "here" a In [10]: import mock In [18]: def test_call_f(): with mock.patch('__main__.f') as mock_f: mock_f.iter.return_value = items call_f() ....: In [19]: test_call_f() --------------------------------------------------------------------------- KeyError Traceback (most recent call last) <ipython-input-19-33ca65a4f3eb> in <module>() ----> 1 test_call_f() <ipython-input-18-92ff5f1363c8> in test_call_f() 2 with mock.patch('__main__.f') as mock_f: 3 mock_f.iter.return_value = items ----> 4 call_f() <ipython-input-8-a5cff08ebf69> in call_f() 1 def call_f(): 2 my_dict = dict(f()) ----> 3 print my_dict[1] KeyError: 1 

Answer 1

Change this line:

 mock_f.iter.return_value = items 

For this:

 mock_f.return_value = iter(items)