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neurologyYou need to know

• Defensive design anticipates how users might accidentally or deliberately misuse a program and reduces the risk of incorrect, unsafe or insecure operation.
• A program should cater for all likely inputs, including valid values, values at permitted limits, invalid values and values of the wrong data type.
• Input validation checks that entered data satisfies predefined rules before the program processes it.
• Common validation checks include range checks, type checks, length checks, presence checks and format checks.
• Validation can reject unsuitable data, but it cannot guarantee that accepted data is factually accurate.
• Invalid input should be rejected with a clear error message and the user should normally be given an opportunity to enter the data again.
• Authentication confirms a user's claimed identity, commonly by checking a username and password against stored credentials.
• Passwords should not be displayed as plain text during entry or stored as plain text because this could expose users' credentials.
• Maintainability is the ease with which a program can be understood, corrected, tested and modified.
• Subprograms divide a program into smaller modules, reducing repetition and allowing individual sections to be developed, tested and reused.
• Meaningful and consistent names for variables, constants and subprograms make their purposes easier to identify.
• Consistent indentation shows the structure of selection, iteration and subprograms, making code easier to read and debug.
• Comments explain the purpose or reasoning behind important sections of code and should add useful information rather than restating obvious instructions.
• Testing is used to find syntax errors, logic errors and unmet requirements before a program is released or used.
• Iterative testing takes place throughout development as individual modules and changes are tested, whereas final or terminal testing checks the completed program at the end of production.
• A syntax error breaks the grammatical rules of a programming language and prevents the program from being translated or run successfully.
• A logic error allows a program to run but causes it to produce an incorrect or unexpected result.
• Normal test data is valid data that the program should accept and process without errors.
• Boundary test data has the correct data type and lies at, or immediately around, the limits of the valid range.
• Invalid test data has the correct data type but should be rejected, whereas erroneous test data has the wrong data type and should also be rejected.

• Anticipate likely accidental and deliberate misuse by identifying risky inputs and designing suitable validation or access controls.
• Design validation routines that check relevant rules, reject unsuitable data with a clear message and allow the user to try again.
• Implement simple authentication by comparing entered credentials with authorised credentials and denying access when they do not match.
• Decompose a program into purposeful subprograms with meaningful names, consistent indentation and appropriate comments.
• Identify syntax errors from code or diagnostic messages and correct the language rules that have been broken.
• Trace a running program to identify logic errors by comparing actual values and outputs with the intended algorithm.
• Select normal, boundary, invalid and erroneous test data for a scenario, including values at and immediately outside each permitted limit.
• Create and complete a test plan containing the test data, test type, reason for the test, expected result, actual result and pass or fail outcome.
• Refine an algorithm or program in response to test results, then retest affected modules and the completed program.