Parametrize with IDs in PyTest - Test Execution Trace

Test Overview

This test uses pytest to run the same test function with different inputs. It uses ids to give each test case a clear name. The test checks if the input number is even.

Test Code - pytest

PyTest

import pytest

@pytest.mark.parametrize(
    "number,expected",
    [
        (2, True),
        (3, False),
        (10, True),
        (7, False)
    ],
    ids=["two", "three", "ten", "seven"]
)
def test_is_even(number, expected):
    assert (number % 2 == 0) == expected

Execution Trace - 7 Steps

Step	Action	System State	Assertion	Result
1	Test starts with pytest runner	pytest ready to run tests	-	PASS
2	pytest collects test_is_even with 4 parameter sets and IDs	Test cases named: test_is_even[two], test_is_even[three], test_is_even[ten], test_is_even[seven]	-	PASS
3	pytest runs test_is_even with number=2, expected=True	Running test_is_even[two]	Check if 2 % 2 == 0 equals True	PASS
4	pytest runs test_is_even with number=3, expected=False	Running test_is_even[three]	Check if 3 % 2 == 0 equals False	PASS
5	pytest runs test_is_even with number=10, expected=True	Running test_is_even[ten]	Check if 10 % 2 == 0 equals True	PASS
6	pytest runs test_is_even with number=7, expected=False	Running test_is_even[seven]	Check if 7 % 2 == 0 equals False	PASS
7	All parameterized tests complete	All tests passed with clear IDs	-	PASS

Failure Scenario

Failing Condition: If the assertion fails for any input, e.g., expecting True but got False

Execution Trace Quiz - 3 Questions

What does the 'ids' parameter do in pytest parametrize?

A Gives each test case a readable name

B Changes the test function name

C Skips some test cases

D Runs tests in parallel

Key Result

Using 'ids' in pytest parametrize helps identify each test case clearly in reports, making debugging easier.