Blizzard is preparing to launch the Warcraft III Patch 1.22 Test Servers in upcoming days. It is recommended to install a fresh copy of Warcraft III in a different folder to be used for the test server. Otherwise, you will have to downgrade at the end of the testing.
Karune: The Dev Team is now preparing test servers with the patch that will be available for testing by the public. In order to jump on these servers, you will have to upgrade your version of the game to the test patch. Upon completion of the testing on the public test server, those participating will have to downgrade their version of the game back to the latest retail patch. We will also be using Battle.net forums to gather feedback and bug reports from the community. Exact location of this forum is still to be determined.