1. A method of detecting a change in a signature of Internet application traffic of an Internet application traffic protocol generated between a server and a client in a test automation system, the method comprising the steps of: executing a test script to operate an application of the client; receiving an actual analysis result of analyzing the signature of the Internet application traffic generated according to the operation of the application from a protocol analysis device; comparing the actual analysis result with a predictive analysis result; and detecting whether there is a change in the signature from a comparison result of comparing the actual analysis result with the predictive analysis result; wherein the step of comparing the actual analysis result with the predictive analysis result includes comparing the actual analysis result with the predictive analysis result of analyzing a predictive signature of the Internet application traffic predicted in a state in which there is no change in the signature, and further includes comparing the signature with the predictive signature for each item, wherein the item includes webpage access, webpage login, webmail inquiry, webmail creation, webmail transmission and reception, messenger login, dialogue transmission and reception in a messenger, and file transmission and reception in the messenger.