Ordering tests for parallel safety in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'parallel safety' mean in test ordering?

Parallel safety means tests can run at the same time without interfering with each other or causing failures.

beginner

Why is test ordering important when running tests in parallel?

Because some tests depend on shared resources or states, ordering helps avoid conflicts and ensures tests don't fail due to interference.

intermediate

How can you mark tests in pytest to control their order or grouping for parallel runs?

You can use pytest markers like @pytest.mark.order or group tests with custom markers to control execution order or separate tests that should not run together.

intermediate

What is a common strategy to make tests safe for parallel execution?

Isolate tests by avoiding shared state, use fixtures to set up independent environments, and avoid dependencies between tests.

beginner

How does pytest-xdist help with parallel test execution?

pytest-xdist runs tests in parallel across multiple CPUs or machines, speeding up test runs while requiring tests to be parallel safe.

What happens if tests share state and run in parallel without ordering?

A Tests ignore shared state

B Tests always pass faster

C Tests may fail due to interference

D Tests run sequentially automatically

When tests share state and run in parallel without control, they can interfere and cause failures.

Which pytest feature helps run tests in parallel?

A pytest-mock

B pytest-order

C pytest-cov

D pytest-xdist

pytest-xdist enables parallel test execution across CPUs or machines.

How can you prevent tests from running together if they share resources?

A Use markers to separate them

B Run all tests sequentially

C Ignore test failures

D Use random test order

Markers can group or order tests to avoid running conflicting tests together.

What is a good practice to make tests parallel safe?

A Share global variables

B Isolate test data and environment

C Write tests that depend on each other

D Run tests only on one CPU

Isolating test data and environment prevents interference during parallel runs.

What does @pytest.mark.order do?

A Controls the order tests run

B Runs tests in parallel

C Skips tests

D Mocks test dependencies

@pytest.mark.order sets the sequence in which tests execute.

Explain why ordering tests is important for parallel safety and how pytest helps manage this.

Think about shared resources and how to avoid conflicts.

Describe strategies to make your pytest tests safe to run in parallel.

Focus on isolation and controlling test execution.