Ordering tests for parallel safety in PyTest - Build an Automation Script

Verify tests run in correct order to avoid parallel execution conflicts

Preconditions (3)

Step 1: Create three test functions: test_setup, test_action, test_cleanup

Step 2: Mark test_setup to run first, test_cleanup to run last

Step 3: Run tests in parallel using pytest-xdist with 3 workers

Step 4: Observe the order of test execution and resource conflicts

✅ Expected Result: Tests run in the specified order without resource conflicts or failures caused by parallel execution

Automation Requirements - pytest

Assertions Needed:

Verify test_setup runs before test_action

Verify test_cleanup runs after test_action

Verify no test fails due to resource conflicts

Best Practices:

Use pytest-ordering or pytest-dependency to control test order

Avoid shared mutable state between tests

Use fixtures with proper scope to manage setup and cleanup

Use explicit waits or locks if needed to prevent race conditions

Automated Solution

PyTest

import pytest

@pytest.mark.order(1)
def test_setup():
    global resource
    resource = []
    resource.append('setup done')
    assert 'setup done' in resource

@pytest.mark.order(2)
def test_action():
    resource.append('action done')
    assert resource == ['setup done', 'action done']

@pytest.mark.order(3)
def test_cleanup():
    resource.clear()
    assert resource == []

# To run tests in parallel use:
# pytest -n 3 --dist=loadscope

This script uses the pytest-order plugin to control the order of test execution explicitly. The @pytest.mark.order decorator sets the order: test_setup runs first, test_action second, and test_cleanup last.

The tests share a global resource list to simulate shared state. Each test asserts the expected state to ensure no conflicts occur.

Running with pytest -n 3 enables parallel execution with 3 workers. The ordering ensures tests do not run out of sequence, preventing race conditions.

This approach demonstrates how to safely order tests when running in parallel to avoid conflicts.

Common Mistakes - 3 Pitfalls

Not controlling test order when tests share state

Using global variables without proper synchronization

Assuming tests run sequentially by default

Bonus Challenge

Now add data-driven testing with 3 different resource states to verify ordering safety

Show Hint