I don't see a way to abort a test run once it is started.
Posted Sep 25, 2015
Thank you for the request!
We as well got a lot of requests about this option on the DreamForce 2015. So work on it will start very soon. Release of this improvement is planned in about a month.
Thank you for the request.
We will keep updated you about it!
Posted Dec 5, 2016
I want to inform you that the ability to abort a test-run job is implemented in The Welkin Suite beginning from the 0.29.19 version of the IDE.
If you have any new suggestions, please contact us. We will be happy to hear them.
I'll close the current topic as 'Implemented'.