Rails::Dom::Testing

This gem is responsible for comparing HTML doms and asserting that DOM elements are present in Rails applications. Doms are compared via assert_dom_equal and assert_dom_not_equal. Elements are asserted via assert_dom, assert_dom_encoded, assert_dom_email and a subset of the dom can be selected with css_select. The gem is developed for Rails 4.2 and above, and will not work on previous versions.

Usage

Dom Assertions

assert_dom_equal '<h1>Lingua França</h1>', '<h1>Lingua França</h1>'

assert_dom_not_equal '<h1>Portuguese</h1>', '<h1>Danish</h1>'

Selector Assertions

# implicitly selects from the document_root_element
css_select '.hello' # => Nokogiri::XML::NodeSet of elements with hello class

# select from a supplied node. assert_dom asserts elements exist.
assert_dom document_root_element.at('.hello'), '.goodbye'

# select from a supplied node. assert_not_dom asserts elements do not exist.
assert_not_dom document_root_element.at('.hello'), '.goodbye'

# elements in CDATA encoded sections can also be selected
assert_dom_encoded '#out-of-your-element'

# assert elements within an html email exists
assert_dom_email '#you-got-mail'

The documentation in selector_assertions.rb goes into a lot more detail of how selector assertions can be used.

HTML versions

By default, assertions will use Nokogiri's HTML4 parser.

If Rails::Dom::Testing.default_html_version is set to :html5, then the assertions will use Nokogiri's HTML5 parser. (If the HTML5 parser is not available on your platform, then a NotImplementedError will be raised.)

When testing in a Rails application, the parser default can also be set by setting Rails.application.config.dom_testing_default_html_version.

Some assertions support an html_version: keyword argument which can override the default for that assertion. For example:

# compare DOMs built with the HTML5 parser
assert_dom_equal(expected, actual, html_version: :html5)

# compare DOMs built with the HTML4 parser
assert_dom_not_equal(expected, actual, html_version: :html4)

Please see documentation for individual assertions for more details.

Installation

Add this line to your application's Gemfile:

gem 'rails-dom-testing'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rails-dom-testing

Under the hood the doms are parsed with Nokogiri, and you'll generally be working with these two classes:

Contributing to Rails::Dom::Testing

Rails::Dom::Testing is work of many contributors. You're encouraged to submit pull requests, propose features and discuss issues.

See CONTRIBUTING.

License

Rails::Dom::Testing is released under the MIT License.