How do I control the number of parallel worker processes in Playwright Test?

Answer

Sure, you can control the number of workers at a test level in @playwright/test. It runs tests in parallel by default using multiple worker processes.

To change the number of workers, use the --workers option in the command line or set the workers property in the configuration file. Here's how you can do it:

npx playwright test --workers 4

Or in the configuration file:

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

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

If you want to run tests sequentially, set workers: 1 or use --workers=1 in the command line.

Each worker process has two ids: a unique worker index starting from 1 and a parallel index between 0 and workers - 1. You can access these indices from environment variables process.env.TEST_WORKER_INDEX and process.env.TEST_PARALLEL_INDEX, or through testInfo.workerIndex and testInfo.parallelIndex.

For more details on parallelism in Playwright, check out this blog post.