When debugging a ZKP verifier, make sure to keep checking not just that the proof verifies on valid inputs, but also that the proof verification returns an error on invalid inputs (or with nonsensical tweaks to the verification mechanism).

In zk proofs, there are (2) actors : prover and a verifier. 

The prover convince the verifier without revealing any information. 

The verifier verify that the prover is telling the truth. 

A ZKP verifier must reject both invalid proofs and those with tampered verification.