You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: signature_test.go
    path of file: ./repos/bytom/lib/golang.org/x/crypto/openpgp/packet
    
    the code of the file until where you have to start completion: // Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package packet

import (
	"bytes"
	"crypto"
	"encoding/hex"
	"testing"
)

func TestSignatureRead(t *testing.T) {
	packet, err := Read(readerFromHex(signatureDataH
    
func TestSignUserId(t *testing.T) {
	sig := &Signature{
		SigType:    SigTypeGenericCert,
		PubKeyAlgo: PubKeyAlgoRSA,
		Hash:       0, // invalid hash function
	}

	packet, err := Read(readerFromHex(rsaPkDataHex))
	if err != nil {
		t.Fatalf("failed to deserialize public key: %v", err)
	}
	pubKey := packet.(*PublicKey)

	packet, err = Read(readerFromHex(privKeyRSAHex))
	if err != nil {
		t.Fatalf("failed to deserialize private key: %v", err)
	}
	privKey := packet.(*PrivateKey)

	err = sig.SignUserId("", pubKey, privKey, nil)
	if err == nil {
		t.Errorf("did not receive an error when expected")
	}

	sig.Hash = crypto.SHA256
	err = privKey.Decrypt([]byte("testing"))
	if err != nil {
		t.Fatalf("failed to decrypt private key: %v", err)
	}

	err = sig.SignUserId("", pubKey, privKey, nil)
	if err != nil {
		t.Errorf("failed to sign user id: %v", err)
	}
}