Producing Robust Programs

Robust program

Program that can handle errors and unexpected input without crashing

Defensive design

Designing programs to prevent errors and misuse

Validation

Checking data is sensible and within allowed limits

Verification

Checking data matches original input

Presence check

Ensures data is entered and not left blank

Range check

Ensures data is within a specified range

Type check

Ensures data is of correct data type

Length check

Ensures data is correct length

Format check

Ensures data matches a required pattern (e.g. postcode)

Normal test data

Valid input that should be accepted

Boundary test data

Values at the edge of valid range

Invalid test data

Incorrect data that should be rejected

Erroneous test data

Data that is unreasonable or unexpected

Test plan

Document showing test data and expected outcomes

Expected outcome

Result that should occur if program works correctly

Actual outcome

Result produced by program

Comparison of outcomes

Used to identify errors in program

Debugging

Finding and fixing errors in code

Syntax error

Error in code structure preventing execution

Logic error

Program runs but produces incorrect results

Runtime error

Error occurring during program execution

Authentication

Verifying identity of a user

Password rules

Requirements such as length and complexity

Biometric authentication

Uses fingerprint, face or iris recognition

Captcha

Test to check user is human

Input sanitisation

Removing harmful input (e.g. SQL injection)

Maintainability

Ease of updating and modifying program

Readable code

Code that is easy to understand

Comments

Notes in code explaining functionality

Indentation

Structuring code for readability

Use of meaningful variable names

Improves clarity of code

[EXAM] Difference between validation and verification

Validation checks data is sensible, verification checks data is correct

[EXAM] Why boundary testing is important

Identifies errors at edge values where problems often occur

[EXAM 6] Explain importance of validation

Validation ensures data entered is sensible and within limits, reducing errors and improving reliability of program

[EXAM 6] Explain role of defensive design

Prevents incorrect or malicious input using validation, authentication, and input sanitisation to improve security and reliability

[EXAM 6] Explain importance of testing

Testing ensures a program works correctly by using different types of test data to identify errors before release

[EXAM 6] Explain difference between syntax, logic, and runtime errors

Syntax errors prevent execution, logic errors produce incorrect results, and runtime errors occur during execution

[EXAM 6] Explain importance of readable code

Readable code using comments, indentation, and meaningful names makes programs easier to understand, debug, and maintain