Implement BSON::OrderedHash#dup

lib/bson/ordered_hash.rb

@@ -103,6 +103,15 @@ module BSON
       end
 
       alias :update :merge!
+      
+      def dup
+        result = OrderedHash.new
+        @ordered_keys ||= []
+        @ordered_keys.each do |key|
+          result[key] = self[key]
+        end
+        result
+      end
 
       def inspect
         str = '{'

test/bson/ordered_hash_test.rb

@@ -194,4 +194,11 @@ class OrderedHashTest < Test::Unit::TestCase
     copy[:foo] = 1
     assert copy.keys != @oh.keys
   end
+  
+  def test_dup
+    oh2 = @oh.dup
+    oh2['f'] = 9
+    assert_nil @oh['f']
+    assert_equal ['c', 'a', 'z'], @oh.keys
+  end
 end