In software engineering, the notion of unit testing was successfully introduced and applied. Unit tests are easy manageable tests for small parts of a program – single units. They proved especially useful to capture unwanted changes and side effects during the maintenance of a program, and they grow with the evolution of the program.
Ontologies behave quite differently than program units. As there is no information hiding in ontology engineering, and thus no black box components, at first the idea of unit testing for ontologies seems not applicable. In this paper we motivate the need for unit testing, describe the adaptation to the unit testing approach, and give use cases and examples.