fastest shell script that uses symfony's simple-phpunit. description here: https://betterprogramming.pub/improve-phpunit-performance-by-parallelization-using-liuggio-fastest-ff0abc111078

fastest.sh

#!/usr/bin/env sh

# run phpunit to trigger download in symfony
bin/phpunit --version

if [ $1 ]
then
  find tests/ -name '*Test.php' \
    | grep -i "$1" \
    | vendor/bin/fastest -vv --no-errors-summary 'bin/phpunit {}'
else
  find tests/ -name '*Test.php' \
    | vendor/bin/fastest -vv --no-errors-summary 'bin/phpunit {}'
fi