diff --git a/nsync/tests/test_digest.cc b/nsync/tests/test_digest.cc
new file mode 100644
index 0000000..4815919
--- /dev/null
+++ b/nsync/tests/test_digest.cc
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2012 University of California, Los Angeles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Zhenkai Zhu <zhenkai@cs.ucla.edu>
+ *         Chaoyi Bian <bcy@pku.edu.cn>
+ *	   Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#include <boost/test/unit_test.hpp>
+#include <boost/test/output_test_stream.hpp> 
+using boost::test_tools::output_test_stream;
+
+#include "sync-digest.h"
+#include <iostream>
+#include <sstream>
+
+using namespace Sync;
+using namespace Sync::Error;
+using namespace std;
+using namespace boost;
+
+BOOST_AUTO_TEST_SUITE(DigestTests)
+
+BOOST_AUTO_TEST_CASE (BasicTest)
+{
+  Digest d0;
+  BOOST_REQUIRE (d0.empty ());
+}
+
+BOOST_AUTO_TEST_CASE (DigestGenerationTest)
+{
+  Digest d1;
+  BOOST_CHECK_NO_THROW (d1 << "1\n");
+
+  // without explicit finalizing, Digest will not be complete and printing out will cause assert
+  BOOST_CHECK (d1.empty ());
+
+  // fix hash
+  d1.finalize ();
+  
+  BOOST_CHECK_NO_THROW (d1.getHash ());
+  BOOST_CHECK (!d1.empty ());
+  BOOST_CHECK (d1 == d1);
+
+  BOOST_CHECK_THROW (d1 << "2", DigestCalculationError);
+  
+  output_test_stream output;
+  BOOST_CHECK_NO_THROW (output << d1);
+  // BOOST_CHECK (output.check_length (40, false) );
+  // BOOST_CHECK (output.is_equal ("e5fa44f2b31c1fb553b6021e7360d07d5d91ff5e", true)); // for sha1
+	BOOST_CHECK (output.check_length (64, false) );
+	BOOST_CHECK (output.is_equal ("4355a46b19d348dc2f57c046f8ef63d4538ebb936000f3c9ee954a27460dd865", true)); // for sha256
+}
+
+BOOST_AUTO_TEST_CASE (DigestComparison)
+{
+  Digest d1;
+  BOOST_CHECK_NO_THROW (d1 << "1\n");
+  // BOOST_CHECK_THROW (d1 == d1, DigestCalculationError);
+  BOOST_CHECK_NO_THROW (d1.finalize ());
+  BOOST_CHECK (d1 == d1);
+  
+  Digest d2;
+  BOOST_CHECK_NO_THROW (d2 << "2\n");
+  BOOST_CHECK_NO_THROW (d2.finalize ());
+  BOOST_CHECK (d1 != d2);
+  
+  Digest d3;
+  // istringstream is (string ("e5fa44f2b31c1fb553b6021e7360d07d5d91ff5e")); // real sha-1 for "1\n"
+	istringstream is (string ("4355a46b19d348dc2f57c046f8ef63d4538ebb936000f3c9ee954a27460dd865")); // real sha256 for "1\n"
+  BOOST_CHECK_NO_THROW (is >> d3);
+  BOOST_CHECK (!d3.empty ());
+  BOOST_CHECK (d3 == d1);
+  BOOST_CHECK (d3 != d2);
+
+  istringstream is2 (string ("25fa44f2b31c1fb553b6021e7360d07d5d91ff5e")); // some fake hash
+  BOOST_CHECK_THROW (is2 >> d3, DigestCalculationError); // >> can be used only once
+
+  Digest d4;
+  BOOST_CHECK_THROW (is2 >> d4, DigestCalculationError); // is2 is now empty. empty >> is not allowed
+
+  istringstream is3 (string ("25fa44f2b31c1fb553b6021e7360d07d5d91ff5e")); // some fake hash
+  BOOST_CHECK_NO_THROW (is3 >> d4);
+  
+  BOOST_CHECK (d4 != d1);
+  BOOST_CHECK (d4 != d2);
+  BOOST_CHECK (d4 != d3);
+}
+
+BOOST_AUTO_TEST_SUITE_END()