What is the process of running tests in parallel using Playwright Test?

Answer

Parallel checks in @playwright/test enable running multiple tests simultaneously, making the testing process faster and more efficient. By default, test files run in parallel, with multiple worker processes executing tests concurrently. Each worker process has a unique worker index and a parallel index between 0 and (workers - 1). If a worker process fails and restarts, the new process retains the same parallel index but gets a new worker index.

To control test order in parallel mode, use test.describe.configure() to specify that tests within a file should run in parallel. Keep in mind that each test runs in a separate worker process and cannot share state or global variables with other tests.

To run all tests across all files in fully-parallel mode, set fullyParallel: true in your configuration file or for specific projects. Avoid using serial mode for inter-dependent tests, as it's better to have isolated tests that can run independently.

Limit the number of workers by setting workers: 1 in your configuration file or passing --workers=1 on the command line. This disables parallelism, allowing only one worker at a time.

Control the maximum number of parallel workers using --workers <number> or workers: <number> in the command line or configuration file, respectively. On CI, you might want to limit the number of workers compared to local development environments.

In summary, @playwright/test offers various options for controlling test execution across multiple files and processes while maintaining isolation between individual tests.