ByteArrayOutputStream out = new ByteArrayOutputStream();
entry.writeTo(out); // do not use the pretty writer, it will break the signature
ByteArrayInputStream bais = new ByteArrayInputStream(out.toByteArray());
Document<Entry> entry_doc = abdera.getParser().parse(bais);
entry = entry_doc.getRoot();
assertTrue(sig.verify(entry, null)); // the signature better still be valid
entry.setTitle("Change the title");
assertFalse(sig.verify(entry, null)); // the signature better be invalid