monkeypatch fixture in PyTest - Test Execution Trace

Test Overview

This test uses the monkeypatch fixture in pytest to replace a function temporarily. It verifies that the patched function returns the expected mocked value during the test.

Test Code - pytest

PyTest

import pytest

def get_data():
    return "original data"

def test_monkeypatch_example(monkeypatch):
    def mock_get_data():
        return "mocked data"

    monkeypatch.setattr(__name__, "get_data", mock_get_data)

    result = get_data()
    assert result == "mocked data"

Execution Trace - 7 Steps

Step	Action	System State	Assertion	Result
1	Test starts	pytest test runner initialized	-	PASS
2	pytest injects monkeypatch fixture into test function	monkeypatch object ready to patch attributes	-	PASS
3	Define mock_get_data function returning 'mocked data'	mock_get_data function available in test scope	-	PASS
4	Use monkeypatch.setattr to replace get_data with mock_get_data	get_data function temporarily replaced by mock_get_data	-	PASS
5	Call get_data() which now points to mock_get_data	mock_get_data executes and returns 'mocked data'	Check if returned value is 'mocked data'	PASS
6	Assert that result equals 'mocked data'	Assertion compares expected and actual values	assert result == 'mocked data'	PASS
7	Test ends successfully	monkeypatch reverts changes after test	-	PASS

Failure Scenario

Failing Condition: monkeypatch fails to replace get_data or assertion fails

Execution Trace Quiz - 3 Questions

What does the monkeypatch fixture do in this test?

A Temporarily replaces the get_data function with a mock version

B Runs the original get_data function without changes

C Deletes the get_data function permanently

D Calls get_data twice to compare results

Key Result

Use monkeypatch to safely replace parts of your code during tests without permanent changes, ensuring tests are isolated and predictable.