2.3 Producing Robust Programs

2.3 Producing Robust Programs

1. Input Validation

   • Check made to see if data entered is reasonable
     • Examples: Length check(check if it is the right length), Range check(data is in the specified range) and Presence check(check data is entered into a field).

2. Input Sanitisation

   • removal of unwanted characters

3. Maintainability

   • Programs need to be up to data so they are defensive against attacks

4. Indentation

   • code is indented to group together a function
     • and to make code easier to read

5. Comments

   • inform readers of bugs
     • explain code
       • and stop a line of code from executing

6. Defensive Design

   • An approach to software development that produces robust programs
     • Anticipating misuse
     • Writing maintainable code
     • Testing the code with reliable test data

7. Robust VS. Reliable

   • Robust programs
     • handle unexpected inputs without crashing
   • Reliable programs
     • work as intended under any conditions

8. Anticipating misuse

   • Malicious inputs could hijack a system but input validation and sanitisation prevent this
   • Using a firewall prevents access from outsiders

9. Types if validation check

   • Type check
     • tests the type of data entered like string and boolean
   • Range check
     • tests the data falls in a specified range
   • Presence check
     • checks if data required is present
   • Format check
     • checks if data is meets the right format
   • Length check
     • tests that the number of characters entered is in the allowed range

10. Authentication

    • checking a person is authorised
      • like username and password

11. Syntax errors

    • mistakes in the way the code is written
      • program wont run

12. Logic error

    • mistakes in the logic of a program
      • program will still run but outcome may be different

13. Run time errors

    • errors that occur when the program is running

14. The purpose of testing

    • Bugs are errors in the software
      • bugs are mistakes
    • the purpose of testing is to check the program works under good conditions and cope with errors
    • Iterative testing
      • the testing of code as it is written
    • Final/terminal testing
      • testing the program once all the code has been written

15. Types of test data

    • Valid data-correct data
      • Extreme data