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_select, assert_select_encoded, assert_select_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. WWW: https://github.com/rails/rails-dom-testing