Hidden Tests
A hidden test patch is the part of a historical commit that changed tests. An oracle solution patch is the part of the same commit that changed source code.
The validity invariant is:
base + hidden tests fails
base + hidden tests + oracle patch passes
Hidden tests matter because the agent should not simply read the expected solution. The agent gets the base repository and prompt; the verifier keeps the hidden tests and oracle patch separate.
False positives can happen if path heuristics classify files incorrectly. False negatives can happen when a real fix has no tests in the same commit. PatchGym therefore treats mining as candidate generation and verification as the gate.