In TTCN-3, the components which are in charge of executing test case can be divided into MTC (Main Test Component) and PTC (Parallel Test Component). First, the test system creates MTC to start test execution. Then MTC can create several PTCs to invoke the IUT (Implementation under Test) to execute test case. MTC can also coordinate the execution of PTC according to test flow, and implement intercommunication via message queue mechanism. As TTCN¬3 is an abstract testing language, the interaction between TTCN-3 test system and object under test uses abstract test system interface, and real test system interface is replaced by adapter in test execution.