Equivalence class verification and oracle-free testing using two-layer covering arrays

This short paper introduces a method for verifying equivalence classes for module/unit testing. This is achieved using a two-layer covering array, in which some or all values of a primary covering array represent equivalence classes. A second layer covering array of the equivalence class values is computed, and its values substituted for the equivalence class names in the primary array. It is shown that this method can detect certain classes of errors without a conventional test oracle, and an illustrative example is given.