1. A method for synchronizing execution of a plurality of concurrently executing tests of a distributed simulation which execute in one or more computers which are mutually operatively coupled to one another and which includes one or more circuit simulations and the plurality of tests and a hub through which each of the plurality tests can interact with each of the circuit simulations, the method comprising: including in the hub a central thread, a first local thread and a second local thread, wherein said first local thread has a first thread state which represents a first synchronization state of a first one of said plurality of tests, and wherein said second local thread has a second thread state which represents a second synchronization state of a second one of said plurality of tests; and effecting a change in the first synchronization state by signaling the first local thread to cause a change in the first thread state.