Writing property-based testing models is a challenging task. This article introduces a new tool, Faktory, which is capable of automatically generating an executable property-based testing model from less complicated sources: normal function type specifications, and traditional function calling contracts using pre- and post-conditions. Concretely, Faktory is an Elixir library which from an API annotated with executable calling contracts written using the Corsa contract checking library, automatically generates a property-based testing model in the form of a state machine implemented using the Makina state machine DSL. In the article we illustrate the functionalities of the Faktory tool using a number of examples. The first one shows how to test a functional data structure; the second shows how to improve test-case generation by reusing test results; and in the third example a stateful key-value storage is tested by first deriving an initial test model using Faktory, and then refining the generated model using the Makina model/state machine extension mechanism.