Some documents that are equal but not identical

These tests all pass:

    public void testSiblingOrder() 
      throws SAXException, IOException, ParserConfigurationException {
        
        String expected = "<a><x/><y/></a>";
        String actual = "<a><y/><x/></a>";
        assertXMLEqual("Sibling order seems to count", expected, actual);
        
    }

    public void testNamespacePrefix() 
      throws SAXException, IOException, ParserConfigurationException {
        
        String expected = "<a xmlns='http://www.example.org'><x/></a>";
        String actual = "<pre:a xmlns:pre='http://www.example.org'><pre:x/></pre:a>";
        assertXMLEqual(expected, actual);
        
    }
    
    public void testDOCTYPE() 
      throws SAXException, IOException, ParserConfigurationException {
        
        String expected = "<!DOCTYPE a [<!ATTLIST a b CDATA 'test'>]>\n" +
          "<a><x/></a>";
        String actual = "<a b='test'><x/></a>";
        assertXMLEqual(expected, actual);
        
    }
    
    public void testCommentInProlog() 
      throws SAXException, IOException, ParserConfigurationException {
        
        String expected = "<!-- test -->" +
          "<a><x/></a>";
        String actual = "<a><x/></a>";
        assertXMLEqual(expected, actual);
        
    }

    public void testProcessingInstructionInProlog() 
      throws SAXException, IOException, ParserConfigurationException {
        
        String expected = "<?xml-styleshet type='text/css' href='file.css'?>" +
          "<a><x/></a>";
        String actual = "<a><x/></a>";
        assertXMLEqual(expected, actual);
        
    }