acts_as_martian

XPath matching in Test::Unit

February 12, 2008 | code, rails, ruby, testing, xml

Inspired by an article on adding XPath matching to RSpec. I’m not using RSpec currently, and I also have a need for this functionality in my tests, so I decided to a helper for use in Test::Unit to achieve XPath matching in my tests.

Add a new helper method:
Add the following code to your test/test_helper.rb in order to create the assert_has_xpath method.

#test/test_helper.rb
require 'rexml/document'

# Asserts that the specified xpath matches
# at least once in the given document
def assert_has_xpath (xpath, doc)
  doc = doc.is_a?(REXML::Document) ? doc : REXML::Document.new(doc)
  match = REXML::XPath.match doc, xpath
  assert !match.empty?, "Missing xpath '#{xpath}' in document: #{doc}"
end

Optionally, you can add the above to a module and include it in your test_helper, or in your individual tests.

Use the helper in your tests:
Now, in your tests, you can do something like the following

#model.rb
def to_xml options = {}
  xml = options[:builder] ||= Builder::XmlMarkup.new(options)

  xml.toys{
    xml.toy "ball"
    xml.toy "iPhone"
  }
end

#model_test.rb
def test_create_xml_creates_toys
  model = Model.new
  xml = model.to_xml
  assert_has_xpath "/toys[toy='iPhone']", xml
end

And voila! You now have XPath testing in your Test::Unit tests.