Introduction to Software Testing

Recovery blocks

Recovery blocks

• Force a different algorithm to be used for each version so they reduce the probability of common errors
• However, the design of the acceptance test is difficult as it must be independent of the computation used
• There are problems with this approach for real-time systems because of the sequential operation of the redundant versions

Watch out for “wishful labeling”

• software diversity, expert systems, AI, software engineering
• Also watch out for “proof by definition”:
• fault tolerant = uses redundancy
• safe system = uses monitors & shutdown routines