Constructing test cases for n-wise testing from tree-based test models

In our previous work [17], we proposed a model-based combinatorial testing method, called FOT. It provides a technique to design test-models for combinatorial testing based on extended logic trees. In this paper, we introduce pair-wise testing (and by extension, n-wise testing, where n = 1, 2, ...) to FOT, by developing a technique to construct a test-suite of n-wise strategies from the test models in FOT. We take a "transformation approach" to realize this technique. To construct test suites, this approach first transforms test-models in FOT, represented as extended logic trees, to those in the formats which the existing n-wise testing tools (such as PICT [9], ACTS [30], CIT-BACH [31], etc.) accept to input, and then applies transformed test-models to any of these tools. In this transformation approach, an algorithm, called "flattening algorithm", plays a key role. We prove the correctness of the algorithm, and implement the algorithm to automate such test-suite constructions, providing a tool called FOT-nw (FOT with n-wise). Further, to show the effectiveness of the technique, we conduct a case study, where we apply FOT-nw to design test models and automatically construct test suites of n-wise strategies for an embedded system of stationary services for real-use in industry.