Producing Robust Programs

Producing Robust Programs

1. needs to be robust to:

   • ensure the program works correctly
   • program may be unsecure

2. Defensive design

   • Defensive design means that the program works no matter what
   • What could break my code?
   • Some strategies
     • unnexpected user inputs (e.g name has letters, not numbers)
       • Validation (check what they type in is sensable and reasonable)
         • Type check (correct data type)
           • no numbers in name
         • Length check (right length)
           • not over 30 charcters
         • Format check (certain pattern)
           • dd/mm/yy
         • Range check (number in limits)
           • between 1 and 31
         • Presence check (not left blank)
     • Maintainability code is readable
       • the code makes sense
       • you understand code = less chance of mistakes
       • Comments (explain what code should do)
       • Indentation (readibillitie of the code)
       • Formatting (reuse code to make it condence)
     • Removing/minimise bugs
       • Testing
         • Iterative testing: ongoing throughout programming
         • Final Testing: at end of development, code tested as a whole
         • unintended inputs
       • does the code run as intended?
       • Does it meet the users wants?
       • Test Plans
         • Valid Data?
           • Program should work with valid data
         • Invalid Data?
           • Program should not crash when invalid data is used
         • Borderline
           • number between 10 - 100, type in 100
     • Authentication
       • Usernames and passwords used
         • how many times can people login attempts
         • regular change of password
         • complex passwords
       • Only certain users have access
         • Access rights
         • e.g receptionist does not need access to manegment