Integration Testing Maturity Assessment for Safety Critical Avionics Software

Abstract

Safety-critical software failures lead to serious results such as loss of live or damage to the environment; therefore, safety-critical software verification requires special attention. Avionics system software is one type of safety-critical software. “DO-178C: Software Considerations in Airborne Systems and Equipment Certification” was released in 2011 by RTCA, Inc., (Radio Technical Commission for Aeronautics) which defines processes for aircraft systems software verification and development. On the other hand, there are well-defined guidelines to improve validation and verification processes of software system development, specifically for software testing. TMMI (Test Maturity Model Integration) was produced by TMMI Foundation as a guide for organizations to improve their test processes and product quality. However, avionics system software has own safety-related software characteristics, and TMMI does not specifically address software testing practices of these characteristics. To fill this gap, in this thesis study, first, avionics software characteristics as the base for software testing are identified. Then, processes and practices in DO-178C and TMMI (Release 1.3) documents are compared with each other bi-directionally. Finally, based on the avionics software characteristics and the results of the comparison, a guidance document approach for integration testing maturity is developed. Considering the critical role of integration testing in preventing safety-critical software defects, it is thought that this approach will be useful for evaluating the integration testing processes of avionics software. A case study was implemented to understand the effectiveness and applicability of this approach. Two groups of test engineers from same team tried to assess test processes applied. The first group applied TMMI model and the second group applied TMMI with guidance approach to assess their processes. At the end, it was observed that the guidance approach provided more improvement actions for avionics integration test processes by referring to domain specific needs of avionics software testing.