Playwright Worker Index and Parallel Index

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Playwright is an open-source tool for automating web browsers. In Playwright, "worker" is used for a specific browser instance, such as a Chrome browser instance.

  • "Worker index" refers to the specific worker instance used within a test or automation script.
  • "Parallel index" is a term used to refer to the number of worker instances that are being run in parallel as part of a more extensive test suite. 
  • The purpose of parallel execution is to speed up the overall test suite execution time by running tests in multiple worker instances simultaneously. 
  • The "parallel index" identifies the specific worker instance used in parallel execution.
  • Each worker is assigned a unique worker index and a parallel index between 0 and for worker 1.
  • We can also read the index from process.env.TEST_WORKER_INDEX and process.env.TEST_PARALLEL_INDEX.

Difference

Purpose: The worker index identifies a specific worker instance used in a test or automation script. The parallel index identifies the particular worker instance used in the parallel execution of a test suite.

Number of Instances: The worker index is used to identify a single worker instance, while the parallel index is used to identify a specific worker instance within a set of worker instances being executed in parallel.

Use in Testing: The worker index is used to reference a specific browser instance, while the parallel index coordinates the parallel execution of tests across multiple worker instances.

Execution Speed: A parallel index allows for the acceleration of test suite execution time by executing tests in multiple worker instances simultaneously.

Debugging: The worker index can be used for debugging purposes, such as identifying the specific browser instance in which an error or exception occurred during the test execution. The parallel index can be used for debugging similar execution issues.

   const workerIndex = process.env.WORKER_INDEX || 4;
   const parallelIndex = process.env.PARALLEL_INDEX || 2;
    
  • We can read the worker's index and parallel the env process.