Big fat Stratolaunch plane tests all six of its engines

Remember the "Roc"? The awe-inspiring, gigantic carrier aircraft from Stratolaunch, the company owned by Microsoft cofounder Paul Allen?

Back in June, it was ready to make its first rollout for a series of tests, starting with fuel testing. 

Well, this week the six-engine mothership completed its first round of engine testing, as tweeted by Allen: