Testing Experiences of Safety-Critical Embedded Systems

This paper describes the author's experiences of a test approach that has been used in the development and maintenance of a medical X-ray device used for surgical operations. It describes the activities that are performed during the preparation, execution and reporting phase of the test process, focusing on the test activities taking place in the software and the system part of the development project. Several safety related activities are executed by other disciplines, e.g. the regulatory office or hardware department, but this paper focuses on the daily work of software test engineers and system test engineers: Is their test process comparable to the process followed by other non-safety related projects? What are the specific requirements of the test process in a safety-critical environment? Are the test results documented in the same way? Is the complete system tested with maximum coverage? Are certain test-techniques preferred?