The role of testing in the B formal development process

The B method is a formal approach covering all the software development process, through a series of proved refinement steps. An on going debate in the B community is the removal of some classical verification steps of the design, eg. unit and integration testing: the paper is aimed to support the maintenance of stringent testing policies. We first recall previous work that addresses the general question of the limits of formal methods for ultra high dependability (A. Cohn, 1989; A. Hall, 1990). Then, the discussion is focused on the case of the B method. Although the method significantly contributes to fault avoidance, it is shown that additional verifications are still required throughout the development process, whether inspections or tests