14.2Parallel Execution

Playwright runs tests in parallel by default using worker processes. Each worker gets its own browser instance with isolated contexts.

How Workers Work

Worker 1: login.spec.ts     → runs all tests in file sequentially
Worker 2: checkout.spec.ts  → runs all tests in file sequentially
Worker 3: search.spec.ts    → runs all tests in file sequentially
Worker 4: admin.spec.ts     → runs all tests in file sequentially

By default, tests in the same file run sequentially; tests in different files run in parallel across workers.

// playwright.config.ts
export default defineConfig({
  workers: process.env.CI ? 4 : undefined, // undefined = half CPU cores
  fullyParallel: true,  // Also parallelize tests within a file
});

Controlling Parallelism

// Run specific tests sequentially (e.g., tests that share external state)
test.describe.serial('payment flow', () => {
  test('add to cart', async ({ page }) => { /* ... */ });
  test('enter shipping', async ({ page }) => { /* ... */ });
  test('complete payment', async ({ page }) => { /* ... */ });
});

// Configure workers per project
export default defineConfig({
  projects: [
    { name: 'chromium', use: { browserName: 'chromium' } },
    { name: 'api-tests', testMatch: /.*\.api\.ts/, workers: 8 }, // More workers for API tests
  ],
});