Introductory paper.

This special section is devoted to a selection of papers that originally appeared in two thematic sessions on high-level testing of complex systems at IDPT 2002 and 2003, the 6th and 7th World Conference on Integrated Design and Process Technology, which took place in Pasadena, CA in June 2002 and in Austin, TX in December 2003, respectively. This collection of papers spans a wide panoramic view on the development of testing and validation technology along several dimmensions. It touches on issues such as All seven papers present methods, tools, and case studies that aim at using diverse formal techniques for testing complex systems. [ABSTRACT FROM AUTHOR]