A method and associated apparatus for testing telephone system operation. The method comprising connecting a call agent simulator to a network. Call actions or events are applied from the call agent simulator to the network expected to produce expected results in the network. The telephone system operation is verified by comparing the actual results produced to the expected results. In another aspect, an IP network or a consumer premises equipment is verified using the call agent simulator. In another aspect, the telephone system is a Voice over Internet (VoIP) system.