diff --git a/src/test/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowSynchronizerTest.java b/src/test/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowSynchronizerTest.java
new file mode 100644
index 0000000..aaa9ba4
--- /dev/null
+++ b/src/test/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowSynchronizerTest.java
@@ -0,0 +1,313 @@
+package net.onrc.onos.ofcontroller.flowprogrammer;
+
+import static org.junit.Assert.*;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+
+import io.netty.util.concurrent.Future;
+import net.floodlightcontroller.core.IOFSwitch;
+import net.onrc.onos.graph.GraphDBOperation;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowEntry;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.ISwitchObject;
+import net.onrc.onos.ofcontroller.flowmanager.FlowDatabaseOperation;
+import net.onrc.onos.ofcontroller.util.FlowEntry;
+import net.onrc.onos.ofcontroller.util.FlowEntryId;
+
+import org.easymock.EasyMock;
+import org.easymock.IAnswer;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.openflow.protocol.OFFlowMod;
+import org.openflow.protocol.OFMatch;
+import org.openflow.protocol.OFMessage;
+import org.openflow.protocol.OFStatisticsRequest;
+import org.openflow.protocol.OFType;
+import org.openflow.protocol.statistics.OFFlowStatisticsReply;
+import org.openflow.protocol.statistics.OFStatistics;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest({FlowSynchronizer.class, GraphDBOperation.class, FlowDatabaseOperation.class})
+public class FlowSynchronizerTest {
+	private FlowPusher pusher;
+	private FlowSynchronizer sync;
+	private List<Long> idAdded;
+	private List<Long> idRemoved;
+
+	@Before
+	public void setUp() throws Exception {
+		idAdded = new ArrayList<Long>();
+		idRemoved = new ArrayList<Long>();
+		
+		pusher = EasyMock.createMock(FlowPusher.class);
+		EasyMock.expect(pusher.add(EasyMock.anyObject(IOFSwitch.class), EasyMock.anyObject(OFMessage.class)))
+			.andAnswer(new IAnswer<Boolean>() {
+				@Override
+				public Boolean answer() throws Throwable {
+					OFMessage msg = (OFMessage)EasyMock.getCurrentArguments()[1];
+					if (msg.getType().equals(OFType.FLOW_MOD)) {
+						OFFlowMod fm = (OFFlowMod)msg;
+						if (fm.getCommand() == OFFlowMod.OFPFC_DELETE_STRICT) {
+							idRemoved.add(fm.getCookie());
+						}
+					}
+					return null;
+				}
+			}).anyTimes();
+		EasyMock.expect(pusher.add(EasyMock.anyObject(IOFSwitch.class), EasyMock.anyObject(FlowEntry.class)))
+		.andAnswer(new IAnswer<Boolean>() {
+			@Override
+			public Boolean answer() throws Throwable {
+				FlowEntry flow = (FlowEntry)EasyMock.getCurrentArguments()[1];
+				idAdded.add(flow.flowEntryId().value());
+				return null;
+			}
+		}).anyTimes();
+		EasyMock.replay(pusher);
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	/**
+	 * Test that synchronization doesn't affect anything in case either DB and
+	 * flow table has the same entries.
+	 */
+	@Test
+	public void testStable() {
+		// Create mock of flow table : flow 1
+		IOFSwitch sw = createMockSwitch(new long[] {1});
+		
+		// Create mock of flow entries : flow 1
+		initMockGraph(new long[] {1});
+		
+		// synchronize
+		doSynchronization(sw,100);
+		
+		// check if flow is not changed
+		assertEquals(0, idAdded.size());
+		assertEquals(0, idRemoved.size());
+	}
+
+	/**
+	 * Test that an flow is added in case DB has an extra FlowEntry.
+	 */
+	@Test
+	public void testSingleAdd() {
+		// Create mock of flow table : null
+		IOFSwitch sw = createMockSwitch(new long[] {});
+		
+		// Create mock of flow entries : flow 1
+		initMockGraph(new long[] {1});
+		
+		// synchronize
+		doSynchronization(sw,100);
+		
+		// check if single flow is installed
+		assertEquals(1, idAdded.size());
+		assertTrue(idAdded.contains((long)1));
+		assertEquals(0, idRemoved.size());
+	}
+
+	/**
+	 * Test that an flow is deleted in case switch has an extra FlowEntry.
+	 */
+	@Test
+	public void testSingleDelete() {
+		// Create mock of flow table : flow 1
+		IOFSwitch sw = createMockSwitch(new long[] {1});
+		
+		// Create mock of flow entries : null
+		initMockGraph(new long[] {});
+		
+		// synchronize
+		doSynchronization(sw,100);
+		
+		// check if single flow is deleted
+		assertEquals(0, idAdded.size());
+		assertEquals(1, idRemoved.size());
+		assertTrue(idRemoved.contains((long)1));
+	}
+	
+	/**
+	 * Test that appropriate flows are added and other appropriate flows are deleted
+	 * in case flows in DB are overlapping flows in switch.
+	 */
+	@Test
+	public void testMixed() {
+		// Create mock of flow table : flow 1,2,3
+		IOFSwitch sw = createMockSwitch(new long[] {1,2,3});
+		
+		// Create mock of flow entries : flow 2,3,4,5
+		initMockGraph(new long[] {2,3,4,5});
+		
+		// synchronize
+		doSynchronization(sw,100);
+		
+		// check if two flows {4,5} is installed and one flow {1} is deleted
+		assertEquals(2, idAdded.size());
+		assertTrue(idAdded.contains((long)4));
+		assertTrue(idAdded.contains((long)5));
+		assertEquals(1, idRemoved.size());
+		assertTrue(idRemoved.contains((long)1));
+	}
+	
+
+	@Test
+	public void testMassive() {
+		// Create mock of flow table : flow 0-1999
+		long [] swIdList = new long [2000];
+		for (long i = 0; i < 2000; ++i) {
+			swIdList[(int)i] = i;
+		}
+		IOFSwitch sw = createMockSwitch(swIdList);
+		
+		// Create mock of flow entries : flow 1500-3499
+		long [] dbIdList = new long [2000];
+		for (long i = 0; i < 2000; ++i) {
+			dbIdList[(int)i] = 1500 + i;
+		}
+		initMockGraph(dbIdList);
+
+		// synchronize
+		doSynchronization(sw, 3000);
+		
+		// check if 1500 flows {2000-3499} is installed and 1500 flows {0,...,1499} is deleted
+		assertEquals(1500, idAdded.size());
+		for (long i = 2000; i < 3500; ++i) {
+			assertTrue(idAdded.contains(i));
+		}
+		assertEquals(1500, idRemoved.size());
+		for (long i = 0; i < 1500; ++i) {
+			assertTrue(idRemoved.contains(i));
+		}
+	}
+
+	/**
+	 * Create mock IOFSwitch with flow table which has arbitrary flows.
+	 * @param cookieList List of FlowEntry IDs switch has.
+	 * @return Mock object.
+	 */
+	private IOFSwitch createMockSwitch(long[] cookieList) {
+		IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
+		EasyMock.expect(sw.getId()).andReturn((long)1).anyTimes();
+		
+		List<OFStatistics> stats = new ArrayList<OFStatistics>();
+		for (long cookie : cookieList) {
+			stats.add(createReply(cookie));
+		}
+		
+		@SuppressWarnings("unchecked")
+		Future<List<OFStatistics>> future = EasyMock.createMock(Future.class);
+		try {
+			EasyMock.expect(future.get()).andReturn(stats).once();
+		} catch (InterruptedException e1) {
+			fail("Failed in Future#get()");
+		} catch (ExecutionException e1) {
+			fail("Failed in Future#get()");
+		}
+		EasyMock.replay(future);
+		
+		try {
+			EasyMock.expect(sw.getStatistics(EasyMock.anyObject(OFStatisticsRequest.class)))
+				.andReturn(future).once();
+		} catch (IOException e) {
+			fail("Failed in IOFSwitch#getStatistics()");
+		}
+		
+		EasyMock.replay(sw);
+		return sw;
+	}
+	
+	/**
+	 * Create single OFFlowStatisticsReply object which is actually obtained from switch.
+	 * @param cookie Cookie value, which indicates ID of FlowEntry installed to switch.
+	 * @return Created object.
+	 */
+	private OFFlowStatisticsReply createReply(long cookie) {
+		OFFlowStatisticsReply stat = new OFFlowStatisticsReply();
+		OFMatch match = new OFMatch();
+		
+		stat.setCookie(cookie);
+		stat.setMatch(match);
+		stat.setPriority((short)1);
+
+		return stat;
+	}
+	
+	/**
+	 * Create mock GraphDBOperation and FlowDatabaseOperation to mock DB.
+	 * @param idList List of FlowEntry IDs stored in DB.
+	 */
+	private void initMockGraph(long[] idList) {
+		List<IFlowEntry> flowEntryList = new ArrayList<IFlowEntry>();
+		
+		for (long id : idList) {
+			IFlowEntry entry = EasyMock.createMock(IFlowEntry.class);
+			EasyMock.expect(entry.getFlowEntryId()).andReturn(String.valueOf(id)).anyTimes();
+			EasyMock.replay(entry);
+			flowEntryList.add(entry);
+		}
+		
+		ISwitchObject swObj = EasyMock.createMock(ISwitchObject.class);
+		EasyMock.expect(swObj.getFlowEntries()).andReturn(flowEntryList).once();
+		EasyMock.replay(swObj);
+		
+		GraphDBOperation mockOp = PowerMock.createMock(GraphDBOperation.class);
+		EasyMock.expect(mockOp.searchSwitch(EasyMock.anyObject(String.class))).andReturn(swObj).once();
+		
+		PowerMock.mockStatic(FlowDatabaseOperation.class);
+		for (IFlowEntry entry : flowEntryList) {
+			EasyMock.expect(FlowDatabaseOperation.extractFlowEntry(EasyMock.eq(entry)))
+				.andAnswer(new IAnswer<FlowEntry>() {
+					@Override
+					public FlowEntry answer() throws Throwable {
+						IFlowEntry iflow = (IFlowEntry)EasyMock.getCurrentArguments()[0];
+						long flowEntryId = Long.valueOf(iflow.getFlowEntryId());
+						
+						FlowEntry flow = EasyMock.createMock(FlowEntry.class);
+						EasyMock.expect(flow.flowEntryId()).andReturn(new FlowEntryId(flowEntryId)).anyTimes();
+						EasyMock.replay(flow);
+						return flow;
+					}
+					
+				}).anyTimes();
+			EasyMock.expect(mockOp.searchFlowEntry(EasyMock.eq(new FlowEntryId(entry.getFlowEntryId()))))
+				.andReturn(entry);
+		}
+		PowerMock.replay(FlowDatabaseOperation.class);
+		EasyMock.replay(mockOp);
+		
+		try {
+			PowerMock.expectNew(GraphDBOperation.class, "").andReturn(mockOp);
+		} catch (Exception e) {
+			fail("Failed to create GraphDBOperation");
+		}
+		PowerMock.replay(GraphDBOperation.class);
+	}
+	
+	/**
+	 * Instantiate FlowSynchronizer and sync flows.
+	 * @param sw Target IOFSwitch object
+	 */
+	private void doSynchronization(IOFSwitch sw, long wait) {
+		sync = new FlowSynchronizer();
+		sync.init(pusher);
+		sync.synchronize(sw);
+		
+		try {
+			Thread.sleep(wait);
+		} catch (InterruptedException e) {
+			fail("Failed to sleep");
+		}
+	}
+}