Towards Autonomous Self-Tests at Runtime

Self-adaptive and self-organising (SASO) systems are one promising approach to counter the raising interconnectedness and complexity in technical systems [1]. In particular, decisions about parametrisation, behaviour, and even structure are moved into the responsibility of the systems themselves: from design-time to runtime. This means that hardly all conditions a system may face can be foreseen during development. Consequently, a full test coverage at design-time is seldom possible as well. We argue that such a transfer of decisions to runtime also impacts the approach to test the resulting systems. If conditions, interaction partners, and resulting behaviour occur only at runtime, testing these aspects has to occur at runtime as well. Besides standard functionality tests (e.g. watchdogs), the distributed and component-oriented nature of self-organising systems can be re-used for highly autonomous and adaptive test mechanisms by establishing and dissolving relationships of test-tester pairs at runtime. The basic idea is to augment more static self-tests (i.e. integrated in hardware, or internal software routines) with dynamic tests - ranging from availability tests at the lowest level to comprising tests at the highest level (i.e. verifying that a component has not been taken over by an attacker). Since we want to avoid single points of failure and maintain scalability in large-scale self-organised systems, we propose a fully self-organised approach, the autonomous self-tests. In this article, we sketch a concept to runtime testing in terms of self-tests, briefly summarise the state-of-the-art, and illustrate the idea by means of examples from the smart camera and intrusion detection domains.