This paper addresses the need to integrate formal assertions into the modeling, implementation, and testing of statechart based designs. The paper describes an iterative process for the development and verification of statechart prototype models augmented with statechart assertions using the StateRover tool. The novel aspects of the proposed process include (1) writing formal specifications using statechart assertions, (2) JUnit-based simulation and validation of statechart assertions, (3) JUnit-based simulation and testing of statechart prototype models augmented with statechart assertions, (4) automatic, JUnitbased, white-box testing of statechart prototypes augmented with statechart assertions, and (5) spiral adjustment of model and specification using the test results. We demonstrate the proposed process with a prototype of a safety-critical computer assisted resuscitation algorithm (CARA) software for a casualty intravenous fluid infusion pump.