Test-Driven Approach for Safety-Critical Software Development

Nowadays software control large majority of systems that humankind use. Systems that software is used widely, such as transportation, military, medicine and avionics must be safe during operation. Fail in these critical systems may cause catastrophic results (i.e. loss of human life, loss or severe damage to environment or equipment etc.). In order to avoid failure on safety critical systems or at least mitigate risks detailed testing is required. Many safety critical systems are developed with sequential phases and tested with test last approach. But test last approach is not sufficient when requirements are unclear or changed. To overcome weaknesses of test last approach we propose test driven approach for safety critical software development, regulated by IEC 61508 standard. A systematic analysis of IEC 61508 software requirements against proposed approach showed that the approach directly supports some objectives and partially supports some of them. Supported objectives are safety requirement identification, simple and testable software design, verification and validation. In general introduced approach suits regulated software development well and this paper outlines these details.