2.3 - Producing Robust Programs

• Anticipating misuse • Input sanitisation • Validation • Verification • Authentication • Maintainable code

Planning ahead to take steps against potential misuse

Cleaning up data that has been input by removing non-standard characters

Checking whether input data follows specific criteria to be accepted

Checking whether data that has been entered is correct

Ensuring only authorised users can gain access to a system

Code that is readable for other programmers

• Using comments so others can understand the purpose of each line of code • Indentation to improve readability • Appropriate variable names • Using subprograms to reuse code and make them easier to test

To check that: - Program works correctly no matter what input has been entered - To check there are no errors - User requirements met - Acceptable performance and usability - Unauthorised access prevented

The testing of modules repetitively throughout development

Testing that all modules work together (integration testing) at the end of development

A grammatical mistake or a mistake in the rules of the programming language that means a program can’t run

A mistake by the programmer where the program runs but will display an incorrect or unexpected output

• Normal data • Boundary data • Invalid data • Erroneous

Data that the program should accept without causing errors because it is within the validation limit

Data of the correct type which is on the edge of accepted validation limits.

Data of the correct data type that does not meet the validation rules and shouldn’t be accepted

Data of the wrong data type that the program cannot process and should not accept