As the use of standards within the world of information technology (IT) and telecommunications has increased tremendously during the last decade, so has the need for methods and tools that support the verification and validation of both the standards and their implementations.

This need has been addressed by ISO and CCITT (ITU–T) in the Framework and Methodology of Conformance Testing of Implementations of OSI and CCITT Protocols. The framework has now reached the status of an international standard as ISO/IEC 9646 (or X.290).

The standard introduces the concept of abstract test suites (consisting of abstract test cases), a description of a set of tests that should be executed for a system. The tests should be described using a black box model (i.e., only by controlling and observing using the available interfaces).

The abstract tests are to be described using a formal language rather than using informal natural language. As part of the standard, the language TTCN is defined in order to describe the abstract tests.

The copying of the abstract syntax notation one (ASN.1) definitions from the protocol specification into the test suite in TTCN ensures consistency between the information transferred in the system specification and the test specification. Furthermore, data descriptions made in ASN.1 can be used in specification and description language (SDL), the language defined by ITU–T for specification of complex real-time applications (for more information, see the Specification and Description Language (SDL) Web ProForum tutorial). In this way, a tight integration between implementation and test can be achieved.