async def METHOD_NAME(self):
    proof_purpose = CredentialIssuancePurpose()
    with async_mock.patch.object(
        AssertionProofPurpose, "validate"
    ) as validate_mock:
        validate_mock.return_value = PurposeResult(
            valid=True, controller={"id": "random_controller_id"}
        )
        document = TEST_VC_DOCUMENT_SIGNED_ED25519.copy()
        proof = document.pop("proof")
        suite = async_mock.MagicMock()
        verification_method = {"controller": "controller"}
        result = proof_purpose.validate(
            proof=proof,
            document=document,
            suite=suite,
            verification_method=verification_method,
            document_loader=custom_document_loader,
        )
        assert not result.valid
        assert "issuer must match the verification method controller" in str(
            result.error
        )