Test letter is an imitation of a genuine letter. It is usually marked and directed to a fictitious person. [Goode v. United States, 159 U.S. 663, 670-671 (U.S. 1895)]. Such letters are placed in the mails by postal inspectors or officers of the department of justice for the purpose of detecting a post-office employee who is suspected of appropriating letters or their contents. Letters sent through the mails by postal officers to a person suspected of sending prohibited matter through the mails, for purpose of detecting him in such violation of the law are test letters. A test letter is also known as a decoy letter.