The common test of patch 1.7.1 has been rescheduled for tomorrow, Friday, January 17th. We are waiting for the downloads to be ready in the afternoon, and the opening of the servers in the late evening.
You can download the General Test only through the WGC.
If the Common Test is already installed through the WGC, just update it.
If you have WGC, but there is no Common Test client installed, just use this hidden code in the game center itself: