Metamorphic Testing For LLMs: The Oracle Problem's Most Underused Answer

Metamorphic testing (MT) is a practical way to generate test cases and verify results when exact oracles are hard to define. Metamorphic relations (MRs)are fundamental here: expected relationships between multiple inputs and their outputs for the same function or algorithm. As the technique has matured, researchers have explored ways to discover these relations, automate test generation, combine metamorphic testing with other software engineering methods, and use it to validate real systems.