public static void testSignNeg() throws AssertFailException{
        byte[] data = BaseEncoding.base16().lowerCase().decode("CF80CD8AED482D5D1527D7DC72FCEFF84E6326592848447D2DC0B0E87DFC9A90".toLowerCase()); //sha256hash of "testing"
        byte[] sec = BaseEncoding.base16().lowerCase().decode("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF".toLowerCase());

        byte[] resultArr = NativeSecp256k1.sign(data, sec);