Ruby Unit Test : Is this a Valid (well-formed) XML Doc ?

Question

I'm creating an XML document: I want to unit test at least to make sure it's well-formed. So far, I have only been able to approximate this , by using the 'hasElements' in the REXML library.

Is there a better way ? Preferably using built-in libraries (I mean libraries that ship with the standard Ruby 1.8.x distro).

require "test/unit"
require 'rexml/document'
require 'test/unit/ui/console/testrunner'

include REXML

class TestBasic < Test::Unit::TestCase

    def test_createXML
     my_xml=...create doc here...
     doc = Document.new(my_xml);
     assert(doc.has_elements?);
    end

end

Test::Unit::UI::Console::TestRunner.run(TestBasic);

Answer 1

I use LibXML to perform xml validations, here is the basic usage:

require 'libxml'

# parse DTD
dtd = LibXML::XML::Dtd.new(<<EOF)
<!ELEMENT root (item*) >
<!ELEMENT item (#PCDATA) >
EOF

# parse xml document to be validated
instance = LibXML::XML::Document.file('instance.xml')

# validate
instance.validate(dtd) # => true | false

from LibXML::DTD

And this is a link to the LibXML documentation main page.

If you don't want to use your custom validation rules you can still use a public DTD with something like:

require 'open-uri'
dtd =  LibXML::XML::Dtd.new(open("http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd").read)

of course you can do much better :)

Answer 2

You can use Nokogiri. It's not a standard Ruby library, but you can easily install it as a Gem.

begin
  bad_doc = Nokogiri::XML(badly_formed) { |config| config.options = Nokogiri::XML::ParseOptions::STRICT }
rescue Nokogiri::XML::SyntaxError => e
  puts "caught exception: #{e}"
end
# => caught exception: Premature end of data in tag root line 1