@Test
public void testSignMessage() {

    byte[] signedMessage = TransactionEncoder.signMessage(
            createEtherTransaction(), SampleKeys.CREDENTIALS);
    String hexMessage = Numeric.toHexString(signedMessage);
    assertThat(hexMessage,
            is("0xf85580010a840add5355887fffffffffffffff80"
                    + "1c"
                    + "a046360b50498ddf5566551ce1ce69c46c565f1f478bb0ee680caf31fbc08ab727"
                    + "a01b2f1432de16d110407d544f519fc91b84c8e16d3b6ec899592d486a94974cd0"));
}