/**
* verify Signer.getPrivateKey() returns null or private key
*/
public void testGetPrivateKey() throws Exception {
byte [] privateKeyData = { 1, 2, 3, 4, 5};
PrivateKeyStub privateKey = new PrivateKeyStub("private", "fff", privateKeyData);
PublicKeyStub publicKey = new PublicKeyStub("public", "fff", null);
KeyPair kp = new KeyPair(publicKey, privateKey);
Signer s = new SignerStub("sss5");