It is often useful to run formal queries on the ontology (and test instances). This can be compared to unit tests in traditional programming languages: the developer formalizes the possible interpretations of a model by means of queries which are executed on a regular basis. If these queries are formalized in SPARQL, TopBraid Composer's SPIN support can be used to execute them for constraint checking.
Combined with the ability to execute SPIN on top of other reasoners, you can turn TopBraid into a very powerful ontology testing framework.