Electronic interlockings have been replacing conventional interlockings for several years due to the advantages of modern computer technology. However, as in many other software systems, the performance that these systems achieve when operated in a real environment is a problematic issue during the system design. Often poor or even safety critical performance is only detected when systems are installed for field operation. Therefore the performance should be tested prior to the delivery and installation of a system. In this article ideas for testing the performance of electronic interlockings are presented. These methods have been applied successfully to the electronic interlocking ESTW L90 5 of Alcatel.