What is the difference between unittest.mock and patch?

What is the difference between unittest.mock and patch?

unittest.mock is a library for testing in Python that allows you to replace parts of your system under test and make assertions about how they have been used. patch is a decorator or context manager provided by unittest.mock that temporarily replaces the target object with a mock during the test.

Can you give me an example of how to use patch?

Sure! Here's a simple example:

from unittest.mock import patch

def get_data():
    return requests.get('http://example.com/data')

@patch('requests.get')
def test_get_data(mock_get):
    mock_get.return_value.status_code = 200
    response = get_data()
    assert response.status_code == 200

In this example, patch replaces requests.get with a mock object.

When should I use unittest.mock instead of patch?

You would use unittest.mock when you need to create mock objects for testing, while patch is specifically for replacing existing objects with mocks during a test. Use patch when you want to temporarily change the behavior of a specific function or method.

Are there any performance considerations when using mocks?

Yes, using mocks can sometimes slow down your tests if overused or if the mocks are complex. It's best to use them judiciously and only when necessary to isolate the unit of work being tested.