pytest-xdist for parallel execution - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest-xdist parallel test run

Given the following pytest test file and running it with pytest-xdist using 2 workers, what will be the output summary line?

PyTest

import time
import pytest

def test_one():
    time.sleep(1)
    assert True

def test_two():
    time.sleep(1)
    assert True

A 2 passed in ~1 second

B 1 passed, 1 failed in ~1 second

C 2 passed in ~2 seconds

D Tests skipped due to worker error

💡 Hint

Think about how parallel execution affects total test time.

Using pytest-xdist with 2 workers runs tests in parallel, so total time is about the longest single test, not the sum.

❓ assertion

intermediate

Correct assertion for parallel test results

You run pytest with xdist -n 3 on 6 tests. Which assertion correctly checks that all tests passed?

A assert result.testscollected == 3 and result.testsfailed == 0

B assert result.testscollected == 6 and result.testsfailed > 0

C assert result.testscollected == 6 and result.testsfailed == 0

D assert result.testscollected == 0 and result.testsfailed == 0

💡 Hint

Total tests collected is independent of number of workers.

All 6 tests should be collected and none failed if all passed.

🔧 Debug

advanced

Identify cause of flaky test with pytest-xdist

You notice tests sometimes fail when run with pytest-xdist -n 4 but pass when run normally. What is the most likely cause?

A pytest-xdist disables assertions

B pytest-xdist does not support parallel execution

C Tests are too fast to run in parallel

D Tests share and modify global state causing race conditions

💡 Hint

Think about what changes when tests run in parallel.

Parallel tests can interfere if they share mutable global data without isolation.

❓ framework

advanced

Best practice for using pytest-xdist with database tests

When running database tests in parallel with pytest-xdist, what is the best practice to avoid conflicts?

A Disable transactions in tests

B Use separate database instances or schemas per worker

C Use a single shared database connection for all tests

D Run all tests sequentially to avoid conflicts

💡 Hint

Think about how parallel tests can interfere with shared resources.

Isolating database state per worker prevents data conflicts and test interference.

🧠 Conceptual

expert

Understanding pytest-xdist load scheduling modes

pytest-xdist supports different load scheduling modes. Which mode dynamically assigns tests to workers as they finish, improving load balance?

A Load scheduling mode

B Static scheduling mode

C Round-robin scheduling mode

D Batch scheduling mode

💡 Hint

One mode assigns tests dynamically to balance workload.

Load scheduling mode assigns tests to free workers dynamically, reducing idle time.