Handling shared resources in PyTest - Test Execution Trace

Test Overview

This test checks that a shared resource (a simple counter) is correctly reset before each test to avoid interference between tests.

Test Code - pytest

PyTest

import pytest

shared_counter = {'count': 0}

@pytest.fixture(autouse=True)
def reset_counter():
    shared_counter['count'] = 0


def test_increment_once():
    shared_counter['count'] += 1
    assert shared_counter['count'] == 1

def test_increment_twice():
    shared_counter['count'] += 2
    assert shared_counter['count'] == 2

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and loads the test module	shared_counter dictionary initialized with count = 0	-	PASS
2	Before test_increment_once runs, reset_counter fixture sets shared_counter['count'] to 0	shared_counter['count'] is 0	-	PASS
3	test_increment_once increments shared_counter['count'] by 1	shared_counter['count'] is 1	assert shared_counter['count'] == 1	PASS
4	Before test_increment_twice runs, reset_counter fixture sets shared_counter['count'] to 0 again	shared_counter['count'] reset to 0	-	PASS
5	test_increment_twice increments shared_counter['count'] by 2	shared_counter['count'] is 2	assert shared_counter['count'] == 2	PASS

Failure Scenario

Failing Condition: If the reset_counter fixture is missing or not autoused, shared_counter is not reset between tests

Execution Trace Quiz - 3 Questions

What does the reset_counter fixture do before each test?

A Deletes the shared_counter dictionary

B Sets shared_counter['count'] to 0

C Increments shared_counter['count'] by 1

D Does nothing

Key Result

Always reset or isolate shared resources before each test to ensure tests do not affect each other and results stay reliable.