Which of the following describes purposefully injecting extra input during testing, possibly causing an application to crash?

Input validation is a defensive coding practice that sanitizes and checks user input to ensure it meets expected criteria, not a technique for intentionally injecting bad data to crash an application.

Exception handling is a programming construct that gracefully manages errors at runtime, not a testing method that injects malicious or unexpected data.

Application hardening involves reducing the attack surface of software through configuration and patching but is not a testing technique that injects extra input.

Fuzzing involves automatically supplying large volumes of random, unexpected, or invalid data as input to an application to identify weaknesses such as buffer overflows, unhandled exceptions, and denial-of-service conditions. It is specifically designed to discover how an application responds to purposefully malformed input, often revealing bugs that structured manual testing would miss.