Ensuring a correct test result from execution of test cases
requires more than just writing of a test suite. Testing and Test Control
Notation version 3 (TTCN-3) is a standardized test specification and test
implementation language. Its architecture has various entities which
interact by providing and/or requiring services from each other. We
analyze the operations of a TTCN-3 test system and characterize the
properties of these operations. We describe the interactions at a system
level using sequence diagrams followed by a precise and structural
specification of the operations of the TTCN-3 test systems.