Errors and Testing

Errors and Testing

1. Syntax errors

   • When the compiler or interpreter doesn't understand something you've typed because it doesn't follow the rules or grammar of the program
   • Can be diagnosed by compilers meaning they can turn the source code into machine code and a syntax error with its location will be returned

2. Logic errors

   • When the compiler or interpreter is able to run the program but the program does something unexpected
   • More difficult to find
   • Compilers and interpreters won't pick them up
   • Can be found through general use of the program and by systematically testing it using a test plan
   • Trace tables are used to test data

3. Iterative testing

   • The program is tested while being developed
   • Certain modules are tested, errors are fixed, then it is tested again. This process gets repeated until the module is working correctly.
   • Used to identify and fix small errors, preventing larger and more difficult to fix errors later on in the development process

4. Final (terminal) testing

   • The program is tested at the end of the development process. The whole program is tested at the same time to check that it is working correctly.
   • Important as modules may work on their own but errors may occur when modules interact with each other in the program

5. Test plans

   • Will outline exactly what you're going to test and how you're going to test it
   • Will test different types of data
     • Normal data - things that a user is likely to put in
     • Boundary data - values at the limit of what the program should be able to handle
     • Invalid data - inputs with a correct data type that should be rejected by the program
     • Erroneous data - inputs with an incorrect data type that should be rejected by the program
   • Test plans generally use tables to test the data

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