During recent years, considerable research attention has been paid to the employment of ontologies in semantic applications, so the present lack of a comprehensive and global method to ontology evaluation can be a sever obstacle to the field of ontology development. This report reviews the previous ontology evaluation methods especially from the functional perspective, and proposes a new concept named Ontology Testing. Ontology testing is defined as the task-based evaluation of ontologies against a set of competency questions, or other ontology requirements, and it requires the availability of explicit information about the major tasks intended for an ontology. In addition, this report describes how an ontology engineering environment should support ontology testing.