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Section: Application Domains

Automated Boundary Testing from Formal Specifications

In  [7] , we have presented a new approach for test generation from set-oriented formal specifications: the BZ-TT method. This method is based on Constraint Logic Programming (CLP) techniques. The goal is to test every operation of the system at every boundary state using all input boundary values of that operation. It has been validated in several industry case studies for smart card OS and application validation (GSM 11-11 standard [56] and Java Card Virtual Machine Transaction mechanism [59] ) and for embedded automotive software (an automobile wind-screen wiper controller).

This test generation method can be summed up as follows: from the formal model, the system computes boundary values to create boundary states; test cases are generated by traversal of the state space with a preamble part (sequences of operations from the initial state to a boundary state), a body part (critical invocations), an identification part (observation and Oracle state computation) and a post-amble part (return path to initial or boundary state). Then, an executable test script file is generated using a test pattern and a table of correspondence between abstract operations (from the model) and concrete ones. This approach differs in several main points from the work of Dick, Faivre et al : first, using boundary goals as test objectives avoids the complete construction of the reachability graph; second, this process is fully automated and the test engineer could just drive it at the boundary value computation level or for the path computation.

The BZ-TT method is fully supported by the BZ-Testing-Tools tool-set. This environment is a set of tools dedicated to animation and test cases generation from B, Z or State-Chart formal specifications. It is based on the CLPS constraint solver, able to simulate the execution of the specification. By execution, we mean that the solver computes a so-called constrained state by applying the pre- and post-condition of operations. A constrained state is a constraint store where state variables and also input and output variables support constraints.

One orientation of the current work is to go beyond the finiteness assumption limitations by using symbolic constraint propagation during the test generation process and to extend the result to object oriented specifications.


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