diff --git a/tests/data/empty.bson b/tests/data/empty.bson
new file mode 100644
index 0000000..a536906
Binary files /dev/null and b/tests/data/empty.bson differ
diff --git a/tests/data/empty.xml b/tests/data/empty.xml
new file mode 100644
index 0000000..fee7568
--- /dev/null
+++ b/tests/data/empty.xml
@@ -0,0 +1,5 @@
+<twonk>
+<meta/>
+<doc>
+</doc>
+</twonk>
diff --git a/tests/data/smorgasbord.bson b/tests/data/smorgasbord.bson
new file mode 100644
index 0000000..bbd7700
Binary files /dev/null and b/tests/data/smorgasbord.bson differ
diff --git a/tests/data/smorgasbord.xml b/tests/data/smorgasbord.xml
new file mode 100644
index 0000000..b543c2d
--- /dev/null
+++ b/tests/data/smorgasbord.xml
@@ -0,0 +1,29 @@
+<twonk>
+<meta/>
+<doc>
+  <oid name="_id">4ea067497065180748000000</oid>
+  <int name="an_int">42</int>
+  <string name="a_string">foo</string>
+  <boolean name="truthiness">true</boolean>
+  <number name="a_float">42.12345</number>
+  <array name="an_array">
+    <string name="0">x</string>
+    <string name="1">y</string>
+    <string name="2">z</string>
+    <doc name="3">
+      <string name="subobject">yup</string>
+    </doc>
+  </array>
+  <date name="now">1231515664416</date>
+  <ref name="dbref">
+    <ns>namespace</ns>
+    <oid>4ea067497065180748010000</oid>
+  </ref>
+  <regex name="regex">
+    <pattern>foobar</pattern>
+    <options></options>
+  </regex>
+  <null name="a_null_value"></null>
+  <code name="$where">this is code</code>
+</doc>
+</twonk>
diff --git a/tests/test_round_trip.rb b/tests/test_round_trip.rb
new file mode 100644
index 0000000..0670222
--- /dev/null
+++ b/tests/test_round_trip.rb
@@ -0,0 +1,137 @@
+HERE = File.dirname(__FILE__)
+$LOAD_PATH[0,0] = File.join(HERE, '..', 'lib')
+require 'mongo'
+require 'rexml/document'
+require 'test/unit'
+
+# For each xml/bson file in the data subdirectory, we turn the XML into an
+# OrderedHash and then test both Ruby-to-BSON and BSON-to-Ruby translations.
+class RoundTripTest < Test::Unit::TestCase
+
+  include XGen::Mongo::Driver
+
+  @@ruby = nil
+
+  def setup
+    unless @@ruby
+      names = Dir[File.join(HERE, 'data', '*.xml')].collect {|f| File.basename(f).sub(/\.xml$/, '') }
+      @@ruby = {}
+      names.each { |name| @@ruby[name] = xml_to_ruby(name) }
+    end
+  end
+
+  def xml_to_ruby(name)
+    File.open(File.join(HERE, 'data', "#{name}.xml")) { |f|
+      doc = REXML::Document.new(f)
+      doc_to_ruby(doc.root.elements['doc'])
+    }
+  end
+
+  def element_to_ruby(e)
+    type = e.name
+    child = e.elements[1]
+    case type
+    when 'oid'
+      ObjectID.from_string(e.text)
+    when 'ref'
+      dbref_to_ruby(e.elements)
+    when 'int'
+      e.text.to_i
+    when 'number'
+      e.text.to_f
+    when 'string', 'code'
+      e.text.to_s
+    when 'boolean'
+      e.text.to_s == 'true'
+    when 'array'
+      array_to_ruby(e.elements)
+    when 'date'
+      Time.at(e.text.to_f / 1000.0)
+    when 'regex'
+      regex_to_ruby(e.elements)
+    when 'null'
+      nil
+    when 'doc'
+      doc_to_ruby(e)
+    else
+      raise "Unknown type #{type} in element with name #{e.attributes['name']}"
+    end
+  end
+
+  def doc_to_ruby(element)
+    oh = OrderedHash.new
+    element.elements.each { |e| oh[e.attributes['name']] = element_to_ruby(e) }
+    oh
+  end
+
+  def array_to_ruby(elements)
+    a = []
+    elements.each { |e|
+      index_str = e.attributes['name']
+      a[index_str.to_i] = element_to_ruby(e)
+    }
+    a
+  end
+
+  def regex_to_ruby(elements)
+    pattern = elements['pattern'].text
+    options_str = elements['options'].text || ''
+
+    options = 0
+    options |= Regexp::IGNORECASE if options_str.include?('i')
+    options |= Regexp::MULTILINE if options_str.include?('m')
+    options |= Regexp::EXTENDED if options_str.include?('x')
+    Regexp.new(pattern, options)
+  end
+
+  def dbref_to_ruby(elements)
+    ns = elements['ns'].text
+    oid_str = elements['oid'].text
+    DBRef.new(nil, nil, nil, ns, ObjectID.from_string(oid_str))
+  end
+
+# DEBUG
+#   def test_foo
+#     $stderr.puts "#{@@ruby['smorgasbord'].class.name}" # DEBUG
+#     $stderr.puts "@@ruby['smorgasbord'] = #{@@ruby['smorgasbord'].inspect.gsub(/, /, ",\n")}" # DEBUG
+#   end
+
+  # Round-trip comparisons of Ruby-to-BSON and back.
+  # * Take the objects that were read from XML
+  # * Turn them into BSON bytes
+  # * Compare that with the BSON files we have
+  # * Turn those BSON bytes back in to Ruby objects
+  # * Turn them back into BSON bytes
+  # * Compare that with the BSON files we have (or the bytes that were already
+  #   generated)
+  def test_round_trip
+    @@ruby.each { |name, obj|
+      File.open(File.join(HERE, 'data', "#{name}.bson"), 'r') { |f|
+        # Read the BSON from the file
+        bson = f.read
+        bson = if RUBY_VERSION >= '1.9'
+                 bson.bytes
+               else
+                 bson.split(//).collect { |c| c[0] }
+               end
+
+        # Turn the Ruby object into BSON bytes and compare with the BSON bytes
+        # from the file.
+        bson_from_ruby = BSON.new.serialize(obj).to_a
+        assert_equal bson.length, bson_from_ruby.length
+        assert_equal bson, bson_from_ruby
+
+        # Turn those BSON bytes back into a Ruby object
+        obj_from_bson = BSON.new.deserialize(ByteBuffer.new(bson_from_ruby))
+        assert_kind_of OrderedHash, obj_from_bson
+
+        # Turn that Ruby object into BSON and compare it to the original BSON
+        # bytes.
+        bson_from_ruby = BSON.new.serialize(obj_from_bson).to_a
+        assert_equal bson.length, bson_from_ruby.length
+        assert_equal bson, bson_from_ruby
+      }
+    }
+  end
+
+end