Hide first run welcome page with jpm test

I am trying to run jpm test for unit testing a browser extension.

I am currently getting test failed due to an unexpected page not being closed. From the logs I can only assume that it is caused by the Firefox + windows 10 welcome page.

Is there a way I can stop this from happening? I am currently calling: jpm test --tbpl --no-copy

This appears to be creating a new temp default profile to use and because of this the win10 welcome screen appears. Then at the end of running the tests the last test gets the error: Should not be any unexpected windows open

Any help would be greatly appreciated.