2.3. Producing Robust Programs

• What is misuse?


  Using the program in a way that was not intended - they could be accidental or deliberate, but code must be written to stop misuse.
• What is an example of misuse?


  Guessing a password too many times in a row.
• What is authentication?


  Method of ensuring someone is who they claim to be, allowing them to access things - they can be usernames and passwords, biometrics, captcha and more.
• What is validation?


  Placing rules on entered data to ensure it is sensible, minimising the number of mistakes users make.
• What are the kinds of checks in validation?

  • Presence check
  • Length check
  • Range check
  • Type check
  • Format check
• What is a presence check?


  Making sure a value is entered and not left blank.
• What is a length check?


  Making sure a data is a required minimum or maximum length.
• What is a range check?


  Making sure a data is within a given set of boundaries.
• What is a type check?


  Making sure data is of the correct data type.
• What is a format check?


  Making sure the data follows a set pattern.
• What is a whitelist in validation?


  A list of allowed data.
• What is a blacklist in validation?


  List of data not allowed.
• What is maintenance?


  Keeping programs running properly, such as correcting bugs and changing programs when needed.
• What are some things that make maintenance easier?

  • Sub routines
  • Naming conventions
  • Comments
  • Indentations
• How can subroutines help maintenance?


  It makes it easier as each one can be tested and changed separately, and makes code easier to follow.
• How is sensible naming beneficial for maintenance?


  It makes it easier for someone else to identify and follow code.
• How can comments help maintenance?


  They make sure someone else can understand what the code is supposed to do.
• How can indentations help maintenance?


  They layout code so it is easier to follow.
• What are the kinds of tests?

  • Iterative testing
  • Final testing
• What are the purposes of testing?


  • Makes sure program meets user requirements
  • Checks program works correctly
  • Finds any bugs present and allows them to be fixed
  • Ensures user likes how it works
  • Checks that security works
• What is iterative testing?


  Test that happens during development - programmer checks that code works as they're making it - each module is tested separately.
• What is final testing?


  A test at the end of development - the user tests the whole program to see if they're happy with it.
• Why is careful data testing needed?


  To make sure nothing is left untested.
• What is normal data?


  Data that should work and produce a correct result.
• What is invalid or erroneous data?


  Data that shouldn't work - system should be able to deal with it without crashing.
• What is boundary data?


  Data at the edges of a range - ensures boundaries are correctly set.
• What is defensive design?


  Any method that is added into the program to ensure it runs correctly without misuse.
• What are examples of defensive design?


  Authentications and validations.