The authors describe the design of a testing environment, called FOREST (formal environment for systematic testing), for communication systems. The proposed method integrates three major strategies: (1) the use of formal description techniques (FDTs), for their formal semantics, which makes them unambiguous; (2) a stepwise approach to generate appropriate test cases for different test stages; and (3) the systematic support of the testing process, from test development to test execution. FOREST consists of four major subsystems. TENT (test sequence generation tool) is a subsystem that generates test cases from the formal specification of the behavior of a given protocol. APRICOT (ASN.1 pre-compiler, coder and test-debugger) is a subsystem that generates test data from the protocol data structures definition. TESPEC (test specification editor) is a tool producing some test specification based on a standardized formalism. The last subsystem, TEXEC (test executor), is a test execution system which consists of an upper tester and a lower tester, and a simulator of the communication medium.>

The testing environment FOREST (formal environment for systematic testing), which uses formal description techniques systematically, has been developed. FOREST generates the TTCN format test sequence from the specification described in SDL. Furthermore, FOREST generates the test data from the protocol data definition described in ASN.1. By using the FOREST system, the test specification and test execution and test report description are achieved systematically. Therefore, the cost of the testing phase of OSI upper layer software development is reduced. In particular, the facility for test sequence generation of FOREST realizes high coverage with a reasonable cost. The facility can efficiently check protocol specifications. The effectiveness of the approach is demonstrated by an application to the test design for the CCR protocol.>