1) Install this plugin just to make testing easier: https://github.com/catalyst/moodle-tool_testtasks 2) Run cron to completion just to make sure it is empty. The next steps need to be done relatively quickly withing the next minute  php admin/cli/cron.php  3) In terminal 1 queue up a 5 second task (5 to make it easy to just around tabs quick enough) php admin/tool/testtasks/cli/queue_adhoc_tasks.php -d= 5 -n= 1 4) In terminal 2 start cron, it should start processing the 5 second task above php admin/cli/cron.php 5) Quickly jump back to terminal 1 and queue up a second 5 second task php admin/tool/testtasks/cli/queue_adhoc_tasks.php -d= 5 -n= 1 6) Confirm that both 5 seconds tasks are processed