The Turing Test, invented by Alan Turing, is a test designed to evaluate a putative artificial intelligence. It assumes that if a computer cannot be distinguished from a human by a human, by means of dialogue, it is intelligent.
The setup of the test is that an operator can communicate, by means of computer text, to two agents, one computer, one human. The only communication he receives from them is written, and he has no prior contact with either the computer or the human. Both agents must then try to convince the operator that they are the human, and the other is the computer. If the computer can successfully deceive the operator a reliable number of times then it is considered intelligent. No computer has ever passed the test.