1. A method of simulating a trunk gateway for use in testing a telecommunications switch, the method comprising the steps of: receiving a plurality of messages intended for a trunk gateway from the telecommunications switch; for each of the received messages, creating a message handler in a thread to process the received message by parsing the received message and generating a response message in accordance with the parsed received message, wherein the message handlers process the received messages in parallel with each other; and transmitting each of the response messages to the telecommunications switch.