The controversial EM Drive, which seems to create small amounts of thrust, while bypassing the normal laws of motion, will be tested to much higher precision soon. A team of scientists in Germany is preparing a super-sensitive torsion balance for this purpose.

The trouble with testing the EM drive is that the current small prototypes produce such a low amount of thrust that it's difficult to separate this from mundane, interfering effects, such as ambient electromagnetism and heat caused by power applied to the device.

The preliminary results of the German scientists seem to indicate that heat-caused expansion may account for at least some of the apparent thrust.

Please find a link, below, to an article with further details:

http://www.wired.com/story/a-mythical-form-of-space-propulsion-finally-gets-a-real-test/