We don't have the "Invite Code" for the test server, only testers of Tanki Online have it!
All about the test server: The Test Server
When longer open test server?
You do not need an invite code during mass-testing.
If you speak Russian you can apply for tester position on the Russian forum.
help me and is gold boxes a 100000000
F.A.Q. about gold box: http://en.tankiwiki.com/Gold_Box
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