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