In this final video we are going to tackle the “Must never” and “Must always” cases for requirements. To do so, the use of mathematical analysis is employed to determine if the conditions hold.
In some instances “never” and “always” cases cannot be definitively proven; when this happens there are three alternatives. First, subdivide the model into a smaller unit under test and attempt to prove the condition at that level. Second, determine under what conditions the requirement cannot be proven and then implement guards against those conditions. Or finally, explicitly guard against the condition in your model.