RUBY-121

lib/bson/bson_ruby.rb

@@ -116,7 +116,7 @@ module BSON
         raise InvalidDocument, "Document is too large (#{@buf.size}). BSON documents are limited to 4MB (#{4 * 1024 * 1024})."
       end
       @buf.put_int(@buf.size, 0)
-      self
+      @buf
     end
 
     # Returns the array stored in the buffer.

test/mongo_bson/bson_test.rb

@@ -22,6 +22,12 @@ class BSONTest < Test::Unit::TestCase
 
   include BSON
 
+  def test_serialize_returns_byte_buffer
+    doc = {'doc' => 'hello, world'}
+    bson = BSON.serialize(doc)
+    assert bson.is_a?(ByteBuffer)
+  end
+
   def test_deprecated_bson_module
     doc = {'doc' => 'hello, world'}
     bson = BSON.serialize(doc)