Parametrized fixtures in PyTest - Test Execution Trace

Test Overview

This test uses a parametrized fixture in pytest to run the same test with multiple input values. It verifies that the input number is even.

Test Code - pytest

PyTest

import pytest

@pytest.fixture(params=[2, 4, 6])
def even_number(request):
    return request.param

def test_is_even(even_number):
    assert even_number % 2 == 0, f"{even_number} is not even"

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	pytest test runner initialized	-	PASS
2	pytest collects test_is_even and sees it uses fixture even_number with params [2,4,6]	Test collection complete with 3 test cases generated	-	PASS
3	pytest runs test_is_even with even_number=2	Test function receives even_number=2	assert 2 % 2 == 0	PASS
4	pytest runs test_is_even with even_number=4	Test function receives even_number=4	assert 4 % 2 == 0	PASS
5	pytest runs test_is_even with even_number=6	Test function receives even_number=6	assert 6 % 2 == 0	PASS
6	All parametrized tests passed	Test report shows 3 passed tests	-	PASS

Failure Scenario

Failing Condition: One of the parametrized values is not even, e.g., 3

Execution Trace Quiz - 3 Questions

How many times does the test_is_even run with the given fixture?

A 2 times, skipping the last parameter

B 3 times, once for each parameter

C 1 time only

D 4 times, including an extra default run

Key Result

Parametrized fixtures let you run the same test multiple times with different inputs, improving test coverage with less code.