Defensive design

Defensive design

1. Why it's important

   • Number of bugs is minimised
   • So that errors are identified
   • So the program behaves as expected

2. Validation

   • Presence check
     • Checks that data has been entered
   • Length check
     • Checks that data is the correct length
   • Range check
     • Checks the input falls within a required range
   • Format check
     • Checks data is in the write format
   • Spell check
     • Checks that words have been entered correctly