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.