So NASA has tested this; and

After months of speculation and leaked documents, NASA's long-awaited EM Drive paper has finally been peer-reviewed and published. And it shows that the 'impossible' propulsion system really does appear to work.
Produces a small amount of thrust.  At this point.  For a system that lots of people still say CAN'T work, any thrust is interesting.  And
But the team makes it clear that they also weren't attempting to optimise performance in these tests – all they were doing was trying to prove whether or not the drive really works. So it's likely that the EM Drive could get a lot more efficient still.

I don't get the "But it violates a LAW!" objections.  They aren't actual unbreakable 'laws', they're how we understand things to work based on what we know.  This could be something we didn't know about before showing up.

Speaking of, it could be some weird(or 'another' weird) thing about quantum effects that we didn't know about before because nobody had done a thing that would show it before this.

We'll see.