// Arrange
        when(signingDigest.verify(any(byte[].class), anyInt(), anyInt(), anyInt(), any())).thenReturn(true, false, true, false, true);

        // Act & Assert
        assertTrue(signingDigest.verify(testData, 0, 8, 0, message));
        assertFalse(signingDigest.verify(testData, 0, 8, 0, message));
        assertTrue(signingDigest.verify(testData, 0, 8, 0, message));

     * @throws GeneralSecurityException if Mac cannot be created
     */
    private Mac createMacInstance() throws GeneralSecurityException {
        if (this.closed) {
            throw new IllegalStateException("SigningDigest is closed");
        }
        if (this.signingKey == null) {
            throw new IllegalStateException("Signing key has been wiped");
        }
        Mac m;
        if (this.provider != null) {

                            } else {
                                final byte[] signingKey = auth.getSigningKey(transport.server.encryptionKey);
                                request.digest = new SigningDigest(signingKey, false);
                            }
                        }

                        request.auth = auth;

                        try {

            readBytesCalls++;
            return 20;
        }
    }

    /**
     * SigningDigest spy that records whether sign() was invoked.
     */
    static class TestSigningDigest extends SigningDigest {
        boolean called;
        int lastLength;

        TestSigningDigest() throws SmbException {
            super(new byte[16], false);
        }

            log.trace("macSigningKey:");
            log.trace(Hexdump.toHexString(macSigningKey, 0, macSigningKey.length));
        }
    }

    /**
     * This constructor used to instance a SigningDigest object for
     * signing/verifying SMB using kerberos session key.
     * The MAC Key = concat(Session Key, Digest of Challenge);
     * Because of Kerberos Authentication don't have challenge,

    boolean useUnicode, received, extendedSecurity;
    long responseTimeout = 1;
    int signSeq;
    boolean verifyFailed;
    NtlmPasswordAuthentication auth = null;
    String path;
    SigningDigest digest = null;
    ServerMessageBlock response;

    ServerMessageBlock() {
        flags = (byte) (FLAGS_PATH_NAMES_CASELESS | FLAGS_PATH_NAMES_CANONICALIZED);
        pid = PID;
        batchLevel = 0;

    SmbComBlankResponse key = new SmbComBlankResponse();
    long sessionExpiration = System.currentTimeMillis() + SO_TIMEOUT;
    LinkedList referrals = new LinkedList();
    SigningDigest digest = null;
    LinkedList sessions = new LinkedList();
    ServerData server = new ServerData();
    /* Negotiated values */
    int flags2 = FLAGS2;
    int maxMpxCount = MAX_MPX_COUNT;