monkeypatch.chdir in PyTest

Introduction

We use monkeypatch.chdir to temporarily change the current folder during a test. This helps test code that works with files or folders without changing your real working folder.

Testing a function that reads files from a specific folder.

Checking how your code behaves when run in different directories.

Avoiding side effects by not changing the real current folder during tests.

Running tests that create or delete files in a temporary folder.

Simulating running your program from another folder.

Syntax

PyTest

monkeypatch.chdir(path)

path can be a string or a pathlib.Path object representing the folder to switch to.

This change lasts only during the test function where you use it.

Examples

Change current folder to /tmp and check it.

PyTest

import os

def test_change_dir(monkeypatch):
    monkeypatch.chdir('/tmp')
    assert os.getcwd() == '/tmp'

Use pathlib.Path to change directory.

PyTest

from pathlib import Path

def test_with_pathlib(monkeypatch):
    monkeypatch.chdir(Path('/var'))
    assert Path.cwd() == Path('/var')

Sample Program

This test changes the current folder to /tmp temporarily. It prints the current folder and checks it is /tmp.

PyTest

import os
from pathlib import Path

def test_temp_dir(monkeypatch):
    temp_dir = Path('/tmp')
    monkeypatch.chdir(temp_dir)
    current = Path.cwd()
    print(f'Current directory is: {current}')
    assert current == temp_dir

Important Notes

Always use monkeypatch.chdir inside test functions with the monkeypatch fixture.

It does not change the folder outside the test, so your real environment stays safe.

If the folder does not exist, the test will fail, so ensure the path is valid.

Summary

monkeypatch.chdir temporarily changes the current working directory during a test.

It helps test code that depends on the current folder without side effects.

Use it with the monkeypatch fixture inside pytest test functions.