Avoiding test interdependence in PyTest - Test Execution Trace

Test Overview

This test suite shows two independent tests using pytest. Each test checks a simple math operation without relying on the other test's result. This avoids test interdependence, ensuring tests can run in any order and still pass.

Test Code - pytest

PyTest

import pytest

# Test 1: Check addition

def test_addition():
    result = 2 + 3
    assert result == 5

# Test 2: Check multiplication

def test_multiplication():
    result = 4 * 5
    assert result == 20

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts and discovers test_addition	No tests have run yet	-	PASS
2	test_addition executes: calculates 2 + 3	Calculation done, result = 5	Assert result == 5	PASS
3	Test runner discovers test_multiplication	test_addition passed, no shared state	-	PASS
4	test_multiplication executes: calculates 4 * 5	Calculation done, result = 20	Assert result == 20	PASS

Failure Scenario

Failing Condition: If test_multiplication depended on test_addition's result and test_addition failed

Execution Trace Quiz - 3 Questions

Why is it important that test_addition and test_multiplication do not share data?

A So tests can run in any order without failing

B To make tests run faster

C To reduce the number of tests

D To use less memory

Key Result

Always write tests so they do not depend on each other. Each test should set up and check only its own data. This makes tests reliable and easier to maintain.