3. Execute scenarios
The users of the system work, usually on their own, to try the system by executing the planned scenarios. It is best that users work alone because they are then more likely to use the system in a realistic way and will not be biased by the advice given by requirements engineers. However, requirement engineers should spend some time observing how end-users make use of the system. This can reveal particular problem areas and the coping strategies which users develop for dealing with system features which they find useful but awkward to use.