Make assert_dom_equal ignore insignificant whitespace

lib/rails/dom/testing/assertions/dom_assertions.rb

@@ -3,6 +3,8 @@ module Dom
     module Testing
       module Assertions
         module DomAssertions
+          NODE_PADDING = ' '.freeze
+
           # \Test two HTML strings for equivalency (e.g., equal even when attributes are in another order)
           #
           #   # assert that the referenced method generates the appropriate HTML string
@@ -67,7 +69,55 @@ def equal_attribute?(attr, other_attr)
           private
 
             def fragment(text)
-              Nokogiri::HTML::DocumentFragment.parse(text)
+              Nokogiri::HTML::DocumentFragment.parse(text).tap do |fragment|
+                pad_tags(fragment.children)
+                condense_whitespace(fragment.children)
+              end
+            end
+
+            def pad_tags(node)
+              return node.each { |n| pad_tags(n) } if node.is_a?(Nokogiri::XML::NodeSet)
+              return unless node.element?
+
+              if (previous = node.previous_sibling) && previous.text?
+                previous.content += NODE_PADDING
+              else
+                node.add_previous_sibling(NODE_PADDING)
+              end
+
+              if (first = node.children.first) && first.text?
+                first.content = NODE_PADDING + first.content
+              else
+                node.prepend_child(NODE_PADDING)
+              end
+
+              if (last = node.children.last) && last.text?
+                last.content = NODE_PADDING + last.content
+              else
+                node.add_child(NODE_PADDING)
+              end
+
+              if (after = node.next_sibling) && after.text?
+                after.content += NODE_PADDING
+              else
+                node.add_next_sibling(NODE_PADDING)
+              end
+
+              pad_tags(node.children)
+            end
+
+            def condense_whitespace(node)
+              if node.is_a?(Nokogiri::XML::NodeSet)
+                node.each { |element| condense_whitespace(element) }
+              elsif node.element?
+                condense_whitespace(node.children)
+              elsif node.text?
+                text = node.text
+                text.gsub!(/\s+/, ' ')
+                text.strip!
+
+                text.empty? ? node.remove : node.content = text
+              end
             end
         end
       end

test/dom_assertions_test.rb

@@ -21,6 +21,54 @@ def test_equal_doms_with_different_order_attributes
     assert_dom_equal(attributes, reverse_attributes)
   end
 
+  def test_dom_equal_up_to_whitespace
+    canonical = %{<a><b>hello</b>world</a>}
+    assert_dom_equal(canonical, %{<a>\n<b>hello </b>\nworld</a>})
+    assert_dom_equal(canonical, %{<a> \n <b> hello </b>world</a>})
+    assert_dom_equal(canonical, %{<a> \n <b>hello </b>world\n</a>\n})
+    assert_dom_equal(canonical, %{<a>\n\t<b>hello </b>\n\tworld</a>})
+  end
+
+  def test_dom_equal_with_indentation
+    canonical = %{<a>hello <b>cruel</b> world</a>}
+    assert_dom_equal(canonical, <<-HTML)
+<a>
+  hello
+  <b>cruel</b>
+  world
+</a>
+    HTML
+
+    assert_dom_equal(canonical, <<-HTML)
+<a>
+hello
+<b>cruel</b>
+world
+</a>
+    HTML
+
+    assert_dom_equal(canonical, <<-HTML)
+<a>hello
+  <b>
+    cruel
+  </b>
+  world</a>
+    HTML
+  end
+
+  def test_dom_not_equal_with_interior_whitespace
+    with_space    = %{<a><b>hello world</b></a>}
+    without_space = %{<a><b>helloworld</b></a>}
+    assert_dom_not_equal(with_space, without_space)
+  end
+
+  def test_explicit_processing_of_text_whitespace
+    valid_cdata = %{<script>//<![CDATA[\n1+1\n//]]></script>}
+    incorrect   = %{<script>//<![CDATA[ 1+1 //]]></script>}
+
+    assert_dom_not_equal(incorrect, valid_cdata)
+  end
+
   def test_dom_not_equal
     assert_dom_not_equal('<a></a>', '<b></b>')
   end