In Blade Runner two replicants take the test:
Leon and Rachael. Deckard tells Tyrell that it usually takes 20 to 30 cross-referenced questions to distinguish a replicant. With Rachael it takes more than a hundred. Tyrell said Rachael was special.
The Voight-Kampff machine
A very advanced form of lie detector that measures contractions of the iris muscle and the presence of invisible airborne particles emitted from the body. The bellows were designed for the latter function and give the machine the menacing air of a sinister insect. The VK is used primarily by Blade Runners to determine if a suspect is truly human by measuring the degree of his empathic response through carefully worded questions and statements.
The Voight-Kampff machine is perhaps analogous to (and may have been partly inspired by) Alan Turing's work which propounded an artificial intelligence test — to see if a computer could convince a human (by answering set questions, etc.) that it was another human. The phrase Turing test was popularised by science fiction but was not used until years after Turing's death.