The Test Description Language (TDL) is a standardized testing technology developed and maintained by the European Telecommunication Standards Institute (ETSI) and specifically designed for high-level test specification. 

The process of stepwise development of tests from requirement specifications is well established and used in both, standardization and industry. Methods and languages produced by the Technical Committee Methods for Testing and Specification (TC MTS), such as the Testing and Test Control Notation version 3 (TTCN-3) and the Test Purpose Language (TPLan) have been designed to support this process.

The Test Description Language (TDL) is the newest addition to these methods and languages acting as an intermediator between TPLan for the specification of test purposes and TTCN-3 for the specification of test cases. TDL is designed to bridge the gap between declarative test purpose specifications (what shall be tested?) and imperative test case specifications (how shall it be tested?) by offering a standardized language for the specification of test descriptions. TDL is part of the ongoing activities by MTS related to establish standardised Model-based Testing (MBT) technologies within ETSI and the industry for conducting functional, conformance, and interoperability tests for a wide range of distributed real-time systems, such as telecommunications, Internet of Things (IoT), and Machine-to-Machine (M2M) systems.

TDL aims to ease the development of executable tests by enabling:

  • Specification of easy-to-understand test case descriptions that can be presented in different representation formats suitable for different stakeholders (graphical, textual, user-specific)
  • Development of test cases by testers lacking programming knowledge
  • Iterative test development along all product development phases, from requirements clarification, via design, to system testing
  • Independence from execution languages and platforms and hiding of test case implementation details
  • Integration of automatically generated and manually developed test cases within a common information platform