Examensarbetet är konfidentiellt. This thesis studies what kinds of test materials are needed when testing basic functionalities and supplementary services in the Mobile Services Switching Center (MSC) node in a GSM system. In this context test materials are sets of messages and information elements used when testing the MSC. The interface between the MSC and the Base Station Subsystems (BSS) called the A-interface is used for testing the MSC functionalities and services. The thesis describes present test methods and tools at Nokia MSC&HLR Integration Testing Section, and the inconveniences with these. The thesis examines the applicability of using the test case specification language TTCN for testing the BSS Application Part protocol in the MSC's A-interface, and if certain parts of present testing environment could be replaced by a TTCN testing environment. The thesis also examines if the use of TTCN makes the test result analyzing automatic and if it is possible to use TTCN for further automation of testing. The test suite were implemented using the ITEX editor and the MSC was tested on a UNIX-based workstation. TTCN was found to be feasible for the testing of the BSSAP protocol in MSC's A-interface. Even the analyzing could be performed automatically with the usage of TTCN. It was also found that it is possible to automate this testing by using automatically generated test suites. It is though doubtful if automatic generated test suites make the integration testing more efficient.