There is no such thing as bug-free software! Nevertheless, software is successfully used even in very critical systems. The software development processes have become so mature that it is possible to reduce the number of errors in the software reliably to such an extent that the number of system errors which have their cause in the software have become so small that they are accepted by society. In these safety relevant projects mainly specification-based, efficiency-based and structure-based test design methods are used. Risk-based testing has not played a significant role in this area so far. On the other hand, the complexity and scope of software is also increasing strongly in the safety-relevant area. Trends such as Industry 4.0 and autonomous driving strongly support this development. Under what conditions could risk-based testing take on a more important role in the safety-relevant area in the future? How can this test design technique be improved so that the technique itself can be further disseminated? The following blog post discusses the strengths and weaknesses of risk-based testing and suggests ways to improve the technique itself. An overview of common test design methods can be found in the blogpost Comparison and evaluation of different test design techniques.
ISO 25119: The norm describes the safety requirements for tractors and machinery for agriculture and forestry. The standard is a sector specific implementation of IEC 61508 and consists of 4 parts. Like other functional safety standards, ISO 25119 specifies various levels of criticality. The standard defines the Agricultural Performance Level (AgPL) QM, a – e. The AgPL a to e correspond to the Performance Levels (PL) a to e as defined in ISO13849.
Regarding the software, an SRL (Software Requirement Level) is derived from the AgPL. Chapter 7.3.5 in Part 2 of the standard defines the relationship between AgPL and the SRLs (B, 1, 2, 3). Read more