Producing robust programs

Producing robust programs

1. issues with not producing robust programs

   • program not work
     • users angry
   • data may be compramised
     • data protection act infragment

2. defensive design

   • make program more robust
     • protect against unexpected user input
       • validation - making sure data entered is sensible and reasonable
         • input names - use min/max char, no numbers, etc
       • dob - dd/mm/yyyy
         • nums only
         • max 31, max 12, max 2022
           • max todays date, min 130 years
       • email
         • @, no spaces
       • validation methods
         • type check, correct data type
         • length check
         • format check, certain pattern
         • range check
     • maintainability
       • commenting
         • helps others understand the code
         • figure out logic errors easier
       • indentation
         • easily identify what code belongs to what group
       • formatting
         • using subroutines/functions
         • easier to navigate
         • organised
       • naming conventions
         • naming variables sensibly
         • using constants
     • minimising/removing bugs
     • protect against malicious users
     • testing
       • iterative testing
         • testing throughout development
         • test aspects before moving on to next part
       • final/terminal testing
         • program tested as a whole
         • does it meet client/user requirements
       • test tables
         • valid data
           • should produce an error
         • invalid data
           • should produce expected results
         • borderline
           • data between valid and invaled
             • need to be delt with correctly by program
       • play to break the game
         • do exactly what your not meant to do
         • try all possible hacks/mistakes
     • authentication
       • usernames and passwords
         • has to log on to access things
         • certain people have access to certain things
         • update passwords regularly, complex passwords, limit attempts, etc