py.test parallel execution for CircleCI

circle.yml.fragment

test:
  override:
    - find . -maxdepth 1 -type d -not -name . > test_dirs:
        parallel: true
    - python circle_node_to_dirs.py < test_dirs > test_dirs_for_node:
        parallel: true
    - echo "Testing `cat test_dirs_for_node`":
        parallel: true
    - py.test `cat test_dirs_for_node`:
        parallel: true

circle_node_to_dirs.py

import os, sys, itertools

def test_dir_portion(node_index, node_total, test_dirs):
    for_node = [v for _, v in filter(lambda (index, test_dir): (index % node_total) == node_index, enumerate(test_dirs))]
    return for_node

def main():
    node_index = int(os.environ.get('CIRCLE_NODE_INDEX', 1))
    node_total = int(os.environ.get('CIRCLE_NODE_TOTAL', 1))
    test_dirs = filter(str, sys.stdin.read().split('\n'))
    test_dirs_for_node = test_dir_portion(node_index, node_total, test_dirs)
    print " ".join(test_dirs_for_node)

if __name__ == '__main__':
    main()

See also: https://github.com/jdunck/pytest-circleci/tree/stable-removal