Developing a business critical system can involve considerable difficulties. This paper describes part of a new methodology that tackles this problem using co-evolution of models and prototypes to strengthen the relationship between modelling and testing.
We illustrate how different modelling frameworks, promela/SPIN and B/ProB/AtelierB, can be used to implement this idea. As a way to reinforce integration between modelling ans testing we use model-based tests and trace-driven model checking. As a result we were able to anticipate problems and guide the development of our software in a safer way, increasing our understanding of the system and its reliability.