Reality check: A bridge between systems thinking and system dynamics

System dynamics models are suppose to be more robust than other kinds of simulation models. However, tests of robustness are usually underused and underdocumented. To allow the extensive use of robustness tests, we have included in the Vensim software a language for defining qualitative and quantitative tests, and a facility for automatically executing the tests on a simulation model. Such automatic tests are called Reality Check tests. These tests provide an explicit indication of model quality and an effective way of comparing models.