Use of binary decision diagrams to handle constraints in combinatorial interaction testing

Constraints on test parameters often substantially impact the performance of test case generation for combinatorial interaction testing. This study discusses constraint handling using binary decision diagrams (BDDs). A BDD is a data structure used to represent and manipulate Boolean functions. The core objective of a constraint handler is to verify if a partial test case with unspecified parameter values satisfies the constraints. In the course of generating a test suite, this check is executed a number of times; thus the efficiency of the check significantly affects the overall time required for test case generation. We present two approaches: performing the verification by computing the logical AND of Boolean functions representing all constraint-satisfying full test cases and a given partial test case, and using a new technique to construct a BDD that represents all constraint-satisfying partial test cases.