2.3 Producing Robust Algorithms

A program that is fault-tolerant and difficult to break/crash.

programs should be designed to be robust and to not crash if a user does something unexpected.

• Input sanitisation/validation • Anticipating misuse • Authentication

validation checks such as length checks and format checks can help to avoid causing errors.

assume that users will try to break the program.

using logon systems with passwords to make sure the user is who they say they are.

testing that is carried out during production.

Carried out just before the final program is released.

• Test with erroneous data • Test with valid data • Test with boundary data

Data that is not valid.

Data ‘on the edges’ of being acceptable

Errors that mean your code works but not as intended e.g < instead of >. These will not be picked up by the IDE.

Ensuring that code is easy to follow and repair/improve/edit.

Comments, indentation, meaningful variable names and use sub-routines.