Assert with messages in PyTest - Test Execution Trace

Test Overview

This test checks if the sum of two numbers is correct. It uses an assertion with a message to explain the failure if the sum is wrong.

Test Code - pytest

PyTest

import pytest

def test_sum():
    a = 5
    b = 7
    result = a + b
    assert result == 12, f"Expected sum to be 12 but got {result}"

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	pytest test runner initialized	-	PASS
2	Assign values a=5 and b=7	Variables a and b set in memory	-	PASS
3	Calculate result = a + b	result variable holds value 12	-	PASS
4	Assert that result == 12 with message	Check if result equals 12	Assert result == 12	PASS
5	Test ends successfully	Test passed with no errors	-	PASS

Failure Scenario

Failing Condition: If the sum result is not 12

Execution Trace Quiz - 3 Questions

What does the assertion message do in this test?

A It changes the sum calculation

B It explains why the test failed if the sum is incorrect

C It skips the test if the sum is wrong

D It prints the sum regardless of the test result

Key Result

Always add clear messages to assertions to help quickly understand why a test failed.