Question

I am fairly new to python development and I am not sure what will be the best way to inject mocks into a function for unit testing.

I have a function which looks like:

import exampleModule

def func():
    ls = createList()
    exampleModule.send(ls)

In the above code I want to mock exampleModule.send method.

Should I pass the method as argument to the function? Like:

def func(invokeMethod):
    ls = createList()
    invokeMethod(ls)

And in unit test I can pass the mock. But I do not want the caller to specify the invocation method.

What is the right way of doing it?

Answer 1

You can use mock library by Michael Foord, which is part Python 3. It makes this kind of mocking very convenient. One way of doing it would be:

>>> from mock import patch
>>> import exampleModule
>>>    
>>> def func():
...     ls = []
...     exampleModule.send(ls)
... 
>>> with patch('exampleModule.send') as send:
...     func()
...     assert send.called

Here we use it as a context manager. But you ca also use patch as a decorator. But there are more ways of using mock and it will probably meet all your needs in mocking/stubbing.