Validation

GIGO
Garbage in Garbage out

What could happen?

• Program crash.
• Incorrect output.
• Unexpected results.

Verification/Validation?

Verification: checks if something is correct.
Validation: checks that something is sensible.

Examples:
Email [Validation]
Age [Validation]
Username length [Validation]
Password complexity [Validation]
Password [Verification]
Postcode [Verification]
Number plate [Verification]

5 ways to check input:

• Presence check: Data input present in the required field?
• Length check: Reasonable length?
• Format check: Data input in the correct format?
• Range check: Data input in the correct range?
• Existence check: Data input match a previously recorded value?