Test Center and Test Center 3 have been both successfully merged together on the 6th of December.
How to check it?
Zoom out further than the normal city view by using the
“-” button on your keyboard. You will then view the whole huge city that contains all cities. Later, press on the box around Test Centre 3 and you shall then be zoomed into it.
Enjoy playing with the new TC comers!
* Official source announcing the merge: http://tso-e.com/blog/?p=483