Definition
Plain language
A small program that checks whether a generated test case is actually legal.
As stated in the literature
A checker enforcing a problem's input constraints; used in self-grading pipelines to filter synthetic test inputs before ranking candidate solutions against them.
Also called: validators
Why it matters: Without it, a system can rank its own candidate solutions against illegal test cases and confidently pick the wrong one.
For example, if a problem promises the input list has at most 100,000 numbers, the validator rejects a generated test case containing 200,000.
Heard on the show
“… provenance-aware context processing so the agent knows what came from outside, sandboxed progress validators that check the agent's "I'm not done" claims against an external policy. …”Episode 030 — Why Your AI Agent Won't Stop Working — and Each Model Falls for a Different Trap