how to mock a function in pytest monkeypatch?

Question

I am trying to mock a simple function but I get an AttributeError and have no clue on how to fix it.

def my_function():
    return "original"

def mock_my_function():
    return "mocked"

def test_my_function(monkeypatch):
    monkeypatch.setattr(__name__, 'my_function', mock_my_function)
    assert my_function() == "mocked"

What should I put in __name__'s place to make it work?

Answer 1

The solution is to put your function that you want to test in a different file so that it can behave as a module.

file with functions you want to test (named original_code.py);

def my_function():
    return "original"

file with test (named test_set.py):

import pytest
import original_code

def test_my_function(monkeypatch):
    
    def mock_my_function():
        return "mocked"
    monkeypatch.setattr(original_code, 'my_function', mock_my_function)
    assert original_code.my_function() == "mocked"

structure of the files

|_ original_code.py
|_ test_set.py

this should mock the function named "my_function" with "mock_my_function" defined inside the test

Answer 2

Well, you can do it with setitem()

#! /usr/bin/env python3

def my_function():
    return "original"

def mock_my_function():
    return "mocked"

def test_my_function(monkeypatch):
    monkeypatch.setitem(globals(), 'my_function', mock_my_function)
    assert my_function() == "mocked"