The Manchurian test was a test used by Starfleet doctors in the mid-23rd century. The test consisted of random memory sampling and was deemed highly effective at detecting what used to be called brainwashing, the installation of commands or personality engrams underneath a functioning consciousness. (DIS: "Despite Yourself")
The person believed to be Ash Tyler was submitted to a Manchurian test, as well as a full set of physical scans, upon being rescued from Klingon captivity. Though after the tests he was allowed to return to active duty, Tyler nonetheless proved to be a Klingon agent. (DIS: "Despite Yourself") He was later revealed to be a Klingon altered as per a species reassignment protocol called choH'a'. (DIS: "The War Without, The War Within")
The name of this tests appears to be a tip of the hat to the well known plot device from the novel The Manchurian Candidate.