considered during the The design facilitates decomposition and design activities testing. At all SILs but particularly at 3 and above the following techniques are to be applied in relation to testability: Comprehensive use of failure assertions and pre-conditions to limit the program input space and therefore the number of test cases (R2) Where diverse monitoring is used then it covers the minimum safety requirements (R2) Where state-based design is used then the test coverage of possible states is defined (R2) – ‘impossible’ states should be trapped by assertions. 14 Modification of To ensure the design 7.4.2.4 For all safety integrity levels ensure that design method chosen shall there is evidence that: possess features that facilitate software The software design is modular. modification such as modularity, information The design is maintainable by virtue of its control of complexity and its hiding and encapsulation information hiding features
considered during the design activities The design facilitates decomposition and testing. At all SILs but particularly at 3 and above the following techniques are to be applied in relation to testability: Comprehensive use of failure assertions and pre-conditions to limit the program input space and therefore the number of test cases (R2) Where diverse monitoring is used then it covers the minimum safety requirements (R2) Where state-based design is used then the test coverage of possible states is defined (R2) – ‘impossible’ states should be trapped by assertions. 14 Modification of design To ensure the design method chosen shall possess features that facilitate software modification such as modularity, information hiding and encapsulation 7.4.2.4 For all safety integrity levels ensure that there is evidence that: The software design is modular. The design is maintainable by virtue of its control of complexity and its information hiding features
CASS_TOES_for_software_assessment_IEC_61508-3_2010_-_ABRIDGED_v1.docx