Fix kucaahbe#62: use Nokogiri::HTML::DocumentFragment for parent_scope

lib/rspec-html-matchers/have_tag.rb

@@ -79,7 +79,7 @@ def matches? src, &block
 
       case src
       when String
-        parent_scope = Nokogiri::HTML(src)
+        parent_scope = Nokogiri::HTML::DocumentFragment.parse(src)
         @document    = src
       else
         parent_scope  = src.current_scope

spec/issues_spec.rb

@@ -0,0 +1,16 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'working on github issues' do
+  describe '#62' do # https://github.com/kucaahbe/rspec-html-matchers/issues/62
+    it 'should not have html tag' do
+      expect('<p>My paragraph.</p>').not_to have_tag('html')
+    end
+
+    it 'should not have body tag' do
+      expect('<p>My paragraph.</p>').not_to have_tag('body')
+    end
+  end
+end