In the information systems development field, most research efforts has been devoted to code testing. But nowadays, most work in conceptual modeling assumes that conceptual schemas are executable and, consequently, they can also be tested. Testing a conceptual schema contributes to its validation early in the development, during the requirements engineering phase.Conceptual schemas are the “general knowledge that an information system needs to know”. We use UML/OCL modeling languages to explicitly represent conceptual schemas. In contrast with a sequence of lines of code, conceptual schemas are represented by a set of conceptual elements (entity types, relationship types, integrity constraints, events, etc.). Therefore, there are important differences between testing code and testing conceptual schemas.