"System.arraycopy should throw when dstIndex + len exceeds dst length");
    }

    @Test
    @DisplayName("encode() throws when dstIndex is negative")
    void encodeThrowsWhenDstIndexNegative() {
        byte[] src = makeSeq(3);
        Encodable enc = new ByteEncodable(src, 0, 3);
        byte[] dst = new byte[3];