  This paper develops automated testing and debugging techniques for answer set
solver development. We describe a flexible grammar-based black-box ASP fuzz
testing tool which is able to reveal various defects such as unsound and
incomplete behavior, i.e. invalid answer sets and inability to find existing
solutions, in state-of-the-art answer set solver implementations. Moreover, we
develop delta debugging techniques for shrinking failure-inducing inputs on
which solvers exhibit defective behavior. In particular, we develop a delta
debugging algorithm in the context of answer set solving, and evaluate two
different elimination strategies for the algorithm.
