Basic lexing + parsing of doctypes.

We're doing these the lazy way. I can't be bothered writing patterns/rules for
4 different formats for something such as doctypes.

spec/oga/lexer_spec.rb

@@ -132,4 +132,18 @@ describe Oga::Lexer do
       ]
     end
   end
+
+  context 'doctypes' do
+    example 'lex the HTML5 doctype' do
+      lex('<!DOCTYPE html>').should == [
+        [:T_DOCTYPE, '<!DOCTYPE html>', 1, 1]
+      ]
+    end
+
+    example 'lex a random doctype' do
+      lex('<!DOCTYPE HTML PUBLIC "foobar" "baz">').should == [
+        [:T_DOCTYPE, '<!DOCTYPE HTML PUBLIC "foobar" "baz">', 1, 1]
+      ]
+    end
+  end
 end

spec/oga/parser/html/doctype_spec.rb

@@ -0,0 +1,18 @@
+require 'spec_helper'
+
+describe Oga::Parser::HTML do
+  context 'doctypes' do
+    example 'parse the HTML5 doctype' do
+      doctype = '<!DOCTYPE html>'
+
+      parse_html(doctype).should == s( :document, s(:doctype, doctype))
+    end
+
+    example 'parse an HTML 4 strict doctype' do
+      doctype = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" ' \
+        '"http://www.w3.org/TR/html4/strict.dtd">'
+
+      parse_html(doctype).should == s(:document, s(:doctype, doctype))
+    end
+  end
+end

spec/support/parsing.rb

@@ -20,5 +20,15 @@ module Oga
     def lex(input)
       return Oga::Lexer.new.lex(input)
     end
+
+    ##
+    # Parses the given HTML and returns an AST.
+    #
+    # @param [String] input
+    # @return [Oga::AST::Node]
+    #
+    def parse_html(input)
+      return Oga::Parser::HTML.new.parse(input)
+    end
   end # ParsingHelpers
 end # Oga