Demonstrating model credibility and validity is an integral part of the development process; therefore, we routinely carry out external validation of our models and those developed by others. Any model developed by Heorfy Consulting is subject to extensive testing to establish the internal and the external validity. Thus, we assess model uncertainty due to both parameters and model structure. In order to increase credibility, any model have to perform well in these regards. Model testing and validation is essential at Heorfy Consulting.