A motor insurer

Where the simple bank is for reading, this model is for running. Its five use cases create the model’s three entities (clients, policies, each naming its drivers, and claims), which an execution environment keeps, checking every pre- and post-condition against them as it runs. Process claim is the one to read closely: it waits for the client’s documents against a deadline, screens and prices the claim, and then declines it or has it assessed, paid and the vehicle repaired.

Who answers each lower-level service is a matter of configuration, and hence the same model runs with people, stubs, compiled services or external systems behind them. It ships without a defect, so it can be taken to execution as it is. If one removes one invariant of its requests, a test run finds the defect which lets a claim pay past its cover.