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a pytest plugin for parallel and concurrent testing

Project description


a pytest plugin for parallel and concurrent testing


This plugin makes it possible to run tests quickly using multiprocessing (parallelism) and multithreading (concurrency).


pytest-xdist is great to run tests that:

  1. aren't threadsafe
  2. perform poorly when multithreaded
  3. need state isolation

pytest-parallel is better for some use cases (like Selenium tests) that:

  1. can be threadsafe
  2. can use non-blocking IO for http requests to make it performant
  3. manage little or no state in the Python environment

Put simply, pytest-xdist does parallelism while pytest-parallel does parallelism and concurrency.


  • Python3 version [3.6+]
  • Unix or Mac for --workers
  • Unix, Mac, or Windows for --tests-per-worker


pip install pytest-parallel


  • workers (optional) - max workers (aka processes) to start. Can be a positive integer or auto which uses one worker per core. Defaults to 1.
  • tests-per-worker (optional) - max concurrent tests per worker. Can be a positive integer or auto which evenly divides tests among the workers up to 50 concurrent tests. Defaults to 1.


# runs 2 workers with 1 test per worker at a time
pytest --workers 2

# runs 4 workers (assuming a quad-core machine) with 1 test per worker
pytest --workers auto

# runs 1 worker with 4 tests at a time
pytest --tests-per-worker 4

# runs 1 worker with up to 50 tests at a time
pytest --tests-per-worker auto

# runs 2 workers with up to 50 tests per worker
pytest --workers 2 --tests-per-worker auto


Beginning with Python 3.8, forking behavior is forced on macOS at the expense of safety.

Changed in version 3.8: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes of the subprocess. See bpo-33725.




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