Parallel Testing in Selenium Python with PyTest

As applications grow in complexity, so do their test suites. Running tests sequentially becomes time-consuming and inefficient. That’s where parallel testing comes in—allowing you to run multiple tests simultaneously to drastically reduce execution time. When using Selenium with Python, one of the best tools for this is PyTest with the pytest-xdist plugin.

In this blog, we’ll explore how to implement parallel testing in Selenium Python using PyTest, including setup, usage, and best practices for faster and more scalable automation.


What is Parallel Testing?

Parallel testing is the execution of multiple tests at the same time, either across different browsers, devices, or configurations. It is especially useful for:

Reducing overall test execution time

Accelerating feedback in CI/CD pipelines

Improving resource utilization


Why Use PyTest for Parallel Testing?

PyTest is a powerful test framework that supports fixtures, parameterization, and plugins. With the pytest-xdist plugin, PyTest allows you to run tests in parallel across multiple CPUs or cores using a simple command-line flag.


Setting Up the Environment

Step 1: Install Required Packages

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pip install selenium pytest pytest-xdist

Step 2: Install WebDriver

Download and place the appropriate browser driver (e.g., ChromeDriver) in your system path or configure it in your script.


Sample Test Case

Create a basic test file named test_google.py.


python


# test_google.py

import pytest

from selenium import webdriver

from selenium.webdriver.common.by import By


@pytest.fixture

def driver():

    driver = webdriver.Chrome()

    yield driver

    driver.quit()


def test_google_search(driver):

    driver.get("https://www.google.com")

    driver.find_element(By.NAME, "q").send_keys("Selenium")

    driver.find_element(By.NAME, "q").submit()

    assert "Selenium" in driver.title

You can duplicate this file into multiple test files (e.g., test_bing.py, test_yahoo.py) to better demonstrate parallelism.


Running Tests in Parallel

To run all tests in parallel using 4 workers (threads):


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pytest -n 4

Here, -n 4 tells PyTest to spawn 4 workers and distribute the test functions across them.


Example Output:

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[gw0] PASSED test_google.py::test_google_search

[gw1] PASSED test_bing.py::test_bing_search

[gw2] PASSED test_yahoo.py::test_yahoo_search

[gw3] PASSED test_duckduckgo.py::test_duckduckgo_search

Each worker runs a test independently, significantly cutting down total runtime.


Best Practices for Parallel Testing

Use Fixtures with Scope "function": Shared resources should be isolated per test to avoid conflicts.


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@pytest.fixture(scope="function")

def driver():

    # new driver instance per test

Avoid Global Variables: Since tests run in separate processes, globals can lead to inconsistent results.


Avoid Shared Files/Databases: If your test modifies shared resources, ensure proper locks or isolation.


Use Markers to Control Test Distribution:


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@pytest.mark.smoke

def test_login(): ...

Then run:


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pytest -n 3 -m smoke

Integrate with CI/CD Pipelines: Use parallel testing in GitHub Actions, Jenkins, or GitLab to speed up your build process.


Advantages of Parallel Testing with PyTest

Speed: Complete large test suites in a fraction of the time.

Scalability: Run across multiple machines using --dist loadscope or Dockerized grids.

Flexibility: Control the number of parallel workers for different environments.


Conclusion

Parallel testing in Selenium Python with PyTest is a game-changer for modern test automation. With just a few configurations and the pytest-xdist plugin, you can dramatically speed up test execution, scale your framework, and ensure faster feedback loops in development. As your project and team grow, parallel testing becomes not just a performance booster—but a necessity.


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Read More: Automating Login and Logout with Selenium Python
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