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Parallelism

Introduction​

Playwright Test runs tests in parallel. In order to achieve that, it runs several worker processes that run at the same time. By default, test files are run in parallel. Tests in a single file are run in order, in the same worker process.

You can control the number of parallel worker processes and limit the number of failures in the whole test suite for efficiency.

Worker processes​

All tests run in worker processes. These processes are OS processes, running independently, orchestrated by the test runner. All workers have identical environments and each starts its own browser.

You can't communicate between the workers. Playwright Test reuses a single worker as much as it can to make testing faster, so multiple test files are usually run in a single worker one after another.

Workers are always shutdown after a test failure to guarantee pristine environment for following tests.

Limit workers​

You can control the maximum number of parallel worker processes via command line or in the configuration file.

From the command line:

npx playwright test --workers 4

In the configuration file:

playwright.config.ts
import { defineConfig } from '@playwright/test';

export default defineConfig({
  // Limit the number of workers on CI, use default locally
  workers: process.env.CI ? 2 : undefined,
});

Disable parallelism​

You can disable any parallelism by allowing just a single worker at any time. Either set workers: 1 option in the configuration file or pass --workers=1 to the command line.

npx playwright test --workers=1

Parallelize tests in a single file​

By default, tests in a single file are run in order. If you have many independent tests in a single file, you might want to run them in parallel with test.describe.configure().

Note that parallel tests are executed in separate worker processes and cannot share any state or global variables. Each test executes all relevant hooks just for itself, including beforeAll and afterAll.

import { test } from '@playwright/test';

test.describe.configure({ mode: 'parallel' });

test('runs in parallel 1', async ({ page }) => { /* ... */ });
test('runs in parallel 2', async ({ page }) => { /* ... */ });

Alternatively, you can opt-in all tests into this fully-parallel mode in the configuration file:

playwright.config.ts
import { defineConfig } from '@playwright/test';

export default defineConfig({
  fullyParallel: true,
});

You can also opt in for fully-parallel mode for just a few projects:

playwright.config.ts
import { defineConfig } from '@playwright/test';

export default defineConfig({
  // runs all tests in all files of a specific project in parallel
  projects: [
    {
      name: 'chromium',
      use: { ...devices['Desktop Chrome'] },
      fullyParallel: true,
    },
  ]
});

Serial mode​

You can annotate inter-dependent tests as serial. If one of the serial tests fails, all subsequent tests are skipped. All tests in a group are retried together.

note

Using serial is not recommended. It is usually better to make your tests isolated, so they can be run independently.

import { test, type Page } from '@playwright/test';

// Annotate entire file as serial.
test.describe.configure({ mode: 'serial' });

let page: Page;

test.beforeAll(async ({ browser }) => {
  page = await browser.newPage();
});

test.afterAll(async () => {
  await page.close();
});

test('runs first', async () => {
  await page.goto('https://playwright.dev/');
});

test('runs second', async () => {
  await page.getByText('Get Started').click();
});

Opt out of fully parallel mode​

If your configuration applies parallel mode to all tests using testConfig.fullyParallel, you might still want to run some tests with default settings. You can override the mode per describe:

test.describe('runs in parallel with other describes', () => {
  test.describe.configure({ mode: 'default' });
  test('in order 1', async ({ page }) => {});
  test('in order 2', async ({ page }) => {});
});

Shard tests between multiple machines​

Playwright Test can shard a test suite, so that it can be executed on multiple machines. See sharding guide for more details.

npx playwright test --shard=2/3

Limit failures and fail fast​

You can limit the number of failed tests in the whole test suite by setting maxFailures config option or passing --max-failures command line flag.

When running with "max failures" set, Playwright Test will stop after reaching this number of failed tests and skip any tests that were not executed yet. This is useful to avoid wasting resources on broken test suites.

Passing command line option:

npx playwright test --max-failures=10

Setting in the configuration file:

playwright.config.ts
import { defineConfig } from '@playwright/test';

export default defineConfig({
  // Limit the number of failures on CI to save resources
  maxFailures: process.env.CI ? 10 : undefined,
});

Worker index and parallel index​

Each worker process is assigned two id