Parallel

Playwright · Reference cheat sheet

📋 Overview

Playwright runs tests in parallel across workers and shards. Isolate state, avoid shared mutable resources, and tune workers for CI hardware.

🔧 Core concepts

Each worker gets its own browser; contexts isolate cookies/storage.

💡 Examples

Config:

export default defineConfig({
  fullyParallel: true,
  workers: process.env.CI ? 2 : undefined,
});

Serial describe (order matters):

test.describe.configure({ mode: 'serial' });
test.describe('checkout flow', () => {
  test('add to cart', async ({ page }) => { /* ... */ });
  test('pay', async ({ page }) => { /* ... */ });
});

Sharding in CI:

npx playwright test --shard=1/3
npx playwright test --shard=2/3
npx playwright test --shard=3/3

Limit parallelism for a file:

test.describe.configure({ mode: 'default' }); // file-level sequential workers

Worker index for unique data:

test('unique user', async ({}, testInfo) => {
  const email = `user-${testInfo.parallelIndex}@ex.com`;
});

⚠️ Pitfalls

• Shared DB rows / accounts without unique keys → cross-test collisions.
• workers: 1 everywhere hides local parallelism bugs until CI.
• Serial suites that are unnecessarily long — prefer independent tests.
• Uneven shards when heavy tests cluster in one file.
• Relying on test order outside serial mode.

🔗 Related

• Config
• CI
• Fixtures
• Authentication
• Tracing
• Page object