diff --git a/ruby/tests/encode_decode_test.rb b/ruby/tests/encode_decode_test.rb
new file mode 100644
index 0000000..09581ab
--- /dev/null
+++ b/ruby/tests/encode_decode_test.rb
@@ -0,0 +1,63 @@
+#!/usr/bin/ruby
+
+# generated_code.rb is in the same directory as this test.
+$LOAD_PATH.unshift(File.expand_path(File.dirname(__FILE__)))
+
+require 'generated_code_pb'
+require 'test/unit'
+
+def hex2bin(s)
+  s.scan(/../).map { |x| x.hex.chr }.join
+end
+
+class EncodeDecodeTest < Test::Unit::TestCase
+  def test_discard_unknown
+    # Test discard unknown in message.
+    unknown_msg = A::B::C::TestUnknown.new(:unknown_field => 1)
+    from = A::B::C::TestUnknown.encode(unknown_msg)
+    m = A::B::C::TestMessage.decode(from)
+    Google::Protobuf.discard_unknown(m)
+    to = A::B::C::TestMessage.encode(m)
+    assert_equal '', to
+
+    # Test discard unknown for singular message field.
+    unknown_msg = A::B::C::TestUnknown.new(
+	    :optional_unknown =>
+	    A::B::C::TestUnknown.new(:unknown_field => 1))
+    from = A::B::C::TestUnknown.encode(unknown_msg)
+    m = A::B::C::TestMessage.decode(from)
+    Google::Protobuf.discard_unknown(m)
+    to = A::B::C::TestMessage.encode(m.optional_msg)
+    assert_equal '', to
+
+    # Test discard unknown for repeated message field.
+    unknown_msg = A::B::C::TestUnknown.new(
+	    :repeated_unknown =>
+	    [A::B::C::TestUnknown.new(:unknown_field => 1)])
+    from = A::B::C::TestUnknown.encode(unknown_msg)
+    m = A::B::C::TestMessage.decode(from)
+    Google::Protobuf.discard_unknown(m)
+    to = A::B::C::TestMessage.encode(m.repeated_msg[0])
+    assert_equal '', to
+
+    # Test discard unknown for map value message field.
+    unknown_msg = A::B::C::TestUnknown.new(
+	    :map_unknown =>
+	    {"" => A::B::C::TestUnknown.new(:unknown_field => 1)})
+    from = A::B::C::TestUnknown.encode(unknown_msg)
+    m = A::B::C::TestMessage.decode(from)
+    Google::Protobuf.discard_unknown(m)
+    to = A::B::C::TestMessage.encode(m.map_string_msg[''])
+    assert_equal '', to
+
+    # Test discard unknown for oneof message field.
+    unknown_msg = A::B::C::TestUnknown.new(
+	    :oneof_unknown =>
+	    A::B::C::TestUnknown.new(:unknown_field => 1))
+    from = A::B::C::TestUnknown.encode(unknown_msg)
+    m = A::B::C::TestMessage.decode(from)
+    Google::Protobuf.discard_unknown(m)
+    to = A::B::C::TestMessage.encode(m.oneof_msg)
+    assert_equal '', to
+  end
+end