Conditional parametrize in PyTest

Introduction

Conditional parametrize helps run tests with different inputs only when certain conditions are met. It saves time by skipping unnecessary test cases.

You want to test a function with multiple inputs but only for specific environments.

You need to run some test cases only if a feature flag is enabled.

You want to skip tests for certain input values based on a condition.

You want to run tests differently depending on the Python version or OS.

Syntax

PyTest

import pytest

@pytest.mark.parametrize('input,expected', [
    (1, 2),
    pytest.param(3, 4, marks=pytest.mark.skipif(condition, reason='skip reason'))
])
def test_func(input, expected):
    assert input + 1 == expected

Use pytest.param to add marks like skipif conditionally.

The condition is a Python expression that returns True or False.

Examples

This example always skips the second test case because the condition is True.

PyTest

import pytest

@pytest.mark.parametrize('x,y', [
    (1, 2),
    pytest.param(3, 4, marks=pytest.mark.skipif(True, reason='Always skip'))
])
def test_add(x, y):
    assert x + 1 == y

This example runs the second test case only on Linux systems.

PyTest

import sys
import pytest

@pytest.mark.parametrize('x,y', [
    (1, 2),
    pytest.param(3, 4, marks=pytest.mark.skipif(sys.platform != 'linux', reason='Only run on Linux'))
])
def test_add(x, y):
    assert x + 1 == y

Sample Program

This test runs two cases. The second case runs only if Python version is 3.8 or higher. Otherwise, it is skipped.

PyTest

import sys
import pytest

@pytest.mark.parametrize('num,expected', [
    (1, 2),
    pytest.param(3, 4, marks=pytest.mark.skipif(sys.version_info < (3, 8), reason='Requires Python 3.8+'))
])
def test_increment(num, expected):
    assert num + 1 == expected

if __name__ == '__main__':
    pytest.main(['-v', __file__])

Important Notes

Use pytest.param to add conditions to individual test cases inside parametrize.

Conditions can check environment, Python version, OS, or any runtime info.

Skipping tests helps keep test runs fast and relevant.

Summary

Conditional parametrize lets you run or skip test cases based on conditions.

Use pytest.param with skipif mark inside parametrize.

This helps test only what matters in your current environment.