Parallel execution in CI in PyTest - Build an Automation Script

Run pytest tests in parallel on CI pipeline

Preconditions (3)

Step 1: Configure the CI pipeline to install dependencies including pytest and pytest-xdist

Step 2: Run pytest with the -n option to enable parallel execution, e.g., pytest -n 4

Step 3: Observe the test execution running tests in parallel

Step 4: Verify that all tests pass successfully

Step 5: Check the CI test report for correct test results

✅ Expected Result: Tests run in parallel on 4 workers, all tests pass, and CI shows a successful test report

Automation Requirements - pytest

Assertions Needed:

All tests pass without errors or failures

Test execution time is reduced compared to sequential run

Best Practices:

Use pytest-xdist plugin for parallel execution

Avoid shared state or use fixtures with proper scope to prevent conflicts

Use explicit waits or synchronization if tests interact with shared resources

Configure CI pipeline to install dependencies and run tests with parallel flag

Automated Solution

PyTest

import pytest

# Sample test file: test_sample.py

def test_one():
    assert 1 + 1 == 2

def test_two():
    assert 'hello'.upper() == 'HELLO'

def test_three():
    assert len([1, 2, 3]) == 3

# To run in CI, use the command:
# pytest -n 4 --dist=loadscope

# This requires pytest-xdist installed:
# pip install pytest-xdist

# In CI pipeline script (example):
# python -m pip install -r requirements.txt
# pytest -n 4 --dist=loadscope

The code defines simple pytest tests to demonstrate parallel execution.

We use the -n 4 option with pytest to run tests on 4 parallel workers.

The --dist=loadscope option helps distribute tests by scope to avoid conflicts.

In the CI pipeline, dependencies including pytest and pytest-xdist must be installed before running tests.

This setup reduces total test time by running tests concurrently.

Common Mistakes - 3 Pitfalls

Not installing pytest-xdist plugin in CI environment

Running tests in parallel that share state without isolation

Hardcoding number of workers without considering CI environment resources

Bonus Challenge

Now add data-driven testing with 3 different inputs and run them in parallel in CI

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