It may seem a bit unrealistic but the in-house all-weather wind tunnel will allow Mercedes-Benz to conduct vigorous hot weather testing, normally only available in remote locations around the world, and extreme cold weather testing, also only available in certain parts of the world, right inside the company's laboratories.
This means engineers can watch the test cars more closely, and repeat tests on the spot if need be. It also allows engineers to test the cars during a wider range of driving characteristics, such as during very high speeds, without endangering drivers or anyone else associated with remote testing.
Mercedes-Benz will use the facilities as a pre-road testing measure though. Once the results have been gathered from within the test centre, prototype cars will then be tested in real world conditions all around the world as well.
Take a look at the video below. It's a pretty cool insight that shows the extent of factory testing. The wind tunnel is capable of mimicking anything from a 200km/h hurricane wind force combined with minus 40 degrees Celsius temperatures, or 40-plus temperatures combined with extreme humidity.