Parallel Testing

Automation

// Definition

Running multiple tests concurrently to reduce wall-clock time. Requires test independence — shared state will cause non-deterministic failures.

// Code Example

GitHub ActionsShard tests across parallel jobs

YAML

jobs:
  e2e:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        shard: [1, 2, 3, 4]
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npx playwright test --shard=${{ matrix.shard }}/4

// Related terms

Cross-Browser Testing
Verifying a web application works correctly across different browsers (Chromium, Firefox, WebKit) and versions. Modern frameworks like Playwright cover all three rendering engines from one suite.
Test Suite
A collection of related test cases organised for execution together — usually grouped by feature, layer (unit, integration, e2e), or test type (smoke, regression).
Flaky Test
A test that passes and fails intermittently without any code changes, often caused by timing issues, shared state, async race conditions, or external dependencies. The single largest source of CI noise.

Learn more · TestNG

Chapter 4 · Lesson 1: Parallel Execution — Methods, Classes, Tests, Instances