Use a helper method for transforming CSS ASTs.

spec/oga/css/transformer/classes_spec.rb

@@ -2,34 +2,12 @@ require 'spec_helper'
 
 describe Oga::CSS::Transformer do
   context 'classes' do
-    before do
-      @transformer = described_class.new
-    end
-
     example 'convert a class node without a node test' do
-      @transformer.process(parse_css('.y')).should == s(
-        :axis,
-        'child',
-        s(
-          :test,
-          nil,
-          '*',
-          s(:eq, s(:axis, 'attribute', s(:test, nil, 'class')), s(:string, 'y'))
-        )
-      )
+      transform_css('.y').should == parse_xpath('*[@class="y"]')
     end
 
     example 'convert a class node with a node test' do
-      @transformer.process(parse_css('x.y')).should == s(
-        :axis,
-        'child',
-        s(
-          :test,
-          nil,
-          'x',
-          s(:eq, s(:axis, 'attribute', s(:test, nil, 'class')), s(:string, 'y'))
-        )
-      )
+      transform_css('x.y').should == parse_xpath('x[@class="y"]')
     end
   end
 end

spec/support/parsing.rb

@@ -89,5 +89,17 @@ module Oga
     rescue Racc::ParseError => error
       return error.message
     end
+
+    ##
+    # Parses and transforms a CSS AST into an XPath AST.
+    #
+    # @param [String] css
+    # @return [AST::Node]
+    #
+    def transform_css(css)
+      ast = parse_css(css)
+
+      return Oga::CSS::Transformer.new.process(ast)
+    end
   end # ParsingHelpers
 end # Oga