An application developer receives a report back from the security team showing their automated tools were able to successfully enter unexpected data into the organization's customer service portal, ca

Non-functional testing evaluates aspects like usability, reliability, and scalability rather than focusing on how the system handles invalid or unexpected input data.

Positive testing verifies that the application behaves correctly when given valid, expected inputs - the opposite of what occurred here, where unexpected data was used to cause a crash.

Performance testing measures how a system behaves under load, stress, or specific workloads, not how it handles invalid or unexpected input data.

Negative testing is specifically designed to input data outside the expected parameters - such as unexpected or malicious inputs - to identify how an application responds to invalid conditions. The security team's automated tools sending unexpected data that caused the portal to crash is a classic example of negative testing, often associated with fuzzing or boundary/edge-case testing. This type of testing reveals vulnerabilities in input validation and error handling.