How do I use the unittest mock library to patch functions?

How do I use the unittest mock library to patch functions?

You can use the patch function from the unittest.mock module to replace a function with a mock during tests.

Can you show me a simple example of how to patch a function?

Sure! Here's a basic example:

from unittest.mock import patch

def my_function():
    return 'Original'

@patch('__main__.my_function')
def test_my_function(mock_my_function):
    mock_my_function.return_value = 'Mocked'
    assert my_function() == 'Mocked'

What if I want to patch a method in a class?

You can patch a method in a class similarly. Just specify the class and method path:

@patch('module.ClassName.method_name')
def test_method(mock_method):
    mock_method.return_value = 'Mocked'
    assert instance.method_name() == 'Mocked'

Are there any best practices for using mocks?

Yes! Always use mocks to isolate tests, avoid side effects, and ensure your tests are fast and reliable.