pytest Quick Start Guide

monkeypatch

In some situations, tests need features that are complex or hard to set up in a testing environment, for example:

• Clients to an external resource (for example GitHub's API), where access during testing might be impractical or too expensive
• Forcing a piece of code to behave as if on another platform, such as error handling
• Complex conditions or environments that are hard to reproduce locally or in the CI

The monkeypatch fixture allows you to cleanly overwrite functions, objects, and dictionary entries of the system being tested with other objects and functions, undoing all changes during test teardown. For example: 

import getpassdef user_login(name):    password = getpass.getpass()    check_credentials(name, password)    ...

In this ...