Languages such as Z, VDM, and B specify an operation from a system by using predicate logic to state how the input and state before the operation relates to the output and the state after the operation. A number of authors have considered the problem of automating test generation on the basis of a specification written in such a language. One of the earliest, and most important, approaches to test automation is the DNF method. Here the specification is rewritten to Disjunctive Normal Form and a partition of the input domain is formed from the preconditions of the disjuncts. Test cases are drawn from each subdomain of the partition.

While the DNF approach has many advantages, it may lead to a combinatorial explosion. We have approached this problem in two ways.

• Only transform the specification part of the way to DNF. This approach is inspired by the observation that the transformation to DNF can be more fine grained than is required and thus can expand the specification further than is required. In addition, by only transforming the specification as far as required we reduce the potential for unwanted redundancy in our test suite.
• Produce a classification tree from the specification and combine classes from this tree to form abstract test cases. While the use of all combinations of classes might reproduce the combinatorial explosion found in the DNF approach, the tester can choose to use only some of the combinations.

• R.M. Hierons, M. Harman, and H. Singh, 2003, Automatically generating information from a Z specification to support the Classification Tree Method, 3rd International Conference of B and Z Users, June 4-6, 2003, LNCS volume 2651, pages 388-407.
• R. M. Hierons, S. Sadeghipour, and H. Singh, 2001, Testing a System specified using Statecharts and Z, Information and Software Technology, 43 2, pp. 137-149.
• R.M. Hierons, 1997, Testing from a Z specification, The Journal of Software Testing, Verification, and Reliability, 7 1, pp. 19-33.

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Last updated: 11th August 2004.