Producing Robust Programs 2.3

Producing Robust Programs 2.3

1. Errors and Testing

   • Testing
     • Iterative Testing
       • This happens over time and is repeated throughout the development of the program
     • Final/Terminal testing
       • This is when the product is released and real end users begin using it. Very often, end users find things wrong with systems programmers did not expect
     • Test Data
       • Something which has been specifically identified for use in tests, typically of a computer program
   • Errors
     • Syntax Error
       • An error in the rules/grammar of the language Eg missing colon / spelling mistake
     • Logic Error
       • The program is written to do something other than what the programmer intended Eg Resetting only the first 9 elements in an array instead of all 10.
   • Types of Test data
     • Valid
       • Data that is correct
     • In Range
       • The maximum values of the data that could be entered for example for teenagers 13 - 19
     • Out of Range
       • Values higher or lower than the expect range, for teenagers greater than 19
     • Null Value
       • When no data is entered or left blank to test what happens
     • Invalid
       • Incorrect values such as entering 'Dave' in an age field

2. key terms

   • Data Validation
     • Check to ensure that the data entered is sensible and reasonable. It does not check the accuracy of data
     • Data Validation techniques
       • Check Digit
         • The last one or two digits in a code are used to check the other digits are correct
       • Format Check
         • Checks the data is in the right format
       • length check
         • Checks the data isn't too short or too long
       • Lookup Table
         • Look up acceptable values in a table
   • Data Sanitisation
     • Trims or strips strings, removing unwanted characters to make sure it contains only permitted characters. E.g. Da%ve the % would be removed.
   • Authentication
     • The process of verifying the identify of a user or process
   • Maintainability
     • Updating code so that it is compatible with current requirements
   • Comments
     • To help describe the code and structures in a program using #
   • Indentation
     • Used to show the programs structure e.g. where selection or iteration or functions are used