producing robust programs

producing robust programs

1. defensive design

   • protection against unexpected user inputs
     • validation
       • check input is sensible and reasonable
   • maintainabilty
   • minimising and removing bugs
   • unsure programs run correctly
   • plan all possibilities
   • testing
     • valid
       • will accept the input
     • invalid
       • not accept the input
     • borderline
       • accept but pick random number
   • authentication
     • usernames and passwords
       • passwords up to date and complex
       • limit login attempts
     • access rights
       • stop people accessing information they are not meant to see