Mock objects in python

Question

I am mocking some objects in my unit tests using the python(3.6) unittest built-in library. Unfortunately I am facing some issues when mocking objects. For example I am writing a test for a function defined in a different file. This function creates a new instance of MyClass and I want to replaced that instance with a mock. So I use "patch".

#unit test file

....
@mock.patch('lib.mymodule.MyClass')
def test_myfunction(self, mock_myclass):
  myfunction()
...

#Function file
from lib.mymodule import MyClass

....
def myfunction():
  mc = MyClass
....

This does not work because when the test calls myfunction() it creates a real "MyClass" object and will not use the mock I tried to include using "patch".

However, if I use the class with its full path then the mock is used

import lib.mymodule

....
def myfunction():
  mc = lib.mymodule.MyClass
...

To deal with the issue I have to get rid of this type of import: from ... import ... . Does anybody know another way to deal with the problem?

Thanks in advance

Odd Kviteberg · Accepted Answer · 2021-03-12 15:07:22Z

1

I found the answer

The class needs to be patched regarding where it is being seen or used. In this case it will be:

@mock.patch('lib.module_with_function_file.MyClass')

The same applies when patching modules

answered Mar 12, 2021 at 15:07

Odd Kviteberg

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