When a skip call is encountered by our back-end simulation engine, the message sending part will be skipped for the client for that iteration, even though payload has been successfully generated. This help in simplifying the code structure for the end user. Note that skip() effect will be automatically cleared for the next iteration for the client. However, the iteration result will not counted as a failure if the payload is skipped. If you want to explicitly mark the current client iteration as a failure, you could use assert(false) function.