diff --git a/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceManagerTest.java b/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceManagerTest.java
index 0b9defb..22900cc 100644
--- a/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceManagerTest.java
+++ b/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceManagerTest.java
@@ -7,7 +7,6 @@
 import static org.easymock.EasyMock.expect;
 import static org.easymock.EasyMock.expectLastCall;
 import static org.easymock.EasyMock.replay;
-import static org.easymock.EasyMock.verify;
 
 import java.util.Date;
 
@@ -16,12 +15,12 @@
 import net.floodlightcontroller.core.IOFSwitch;
 import net.floodlightcontroller.core.IUpdate;
 import net.floodlightcontroller.core.module.FloodlightModuleContext;
+import net.floodlightcontroller.core.module.FloodlightModuleException;
 import net.floodlightcontroller.test.FloodlightTestCase;
 import net.floodlightcontroller.util.MACAddress;
 import net.onrc.onos.core.datagrid.IDatagridService;
 import net.onrc.onos.core.datagrid.IEventChannel;
 import net.onrc.onos.core.datagrid.IEventChannelListener;
-import net.onrc.onos.core.intent.MockTopology;
 import net.onrc.onos.core.packet.ARP;
 import net.onrc.onos.core.packet.DHCP;
 import net.onrc.onos.core.packet.Data;
@@ -32,6 +31,7 @@
 import net.onrc.onos.core.registry.IControllerRegistryService;
 import net.onrc.onos.core.topology.ITopologyListener;
 import net.onrc.onos.core.topology.ITopologyService;
+import net.onrc.onos.core.topology.MockTopology;
 
 import org.easymock.EasyMock;
 import org.junit.After;
@@ -51,9 +51,9 @@
     private IPacket pkt0, pkt1, pkt2, pkt3, pkt4;
     private IOFSwitch sw1;
     private long sw1Dpid;
-    private short sw1DevPort;
+    private long sw1DevPort, sw1DevPort2;
     private OnosDeviceManager odm;
-    private OFPacketIn pktIn;
+    private OFPacketIn pktIn, pktIn2;
     private FloodlightModuleContext modContext;
     private ITopologyService networkGraphService;
     private IEventChannel<Long, OnosDevice> eventChannel;
@@ -69,7 +69,7 @@
         IDatagridService datagridService;
         IControllerRegistryService controllerRegistryService;
 
-        topology.createSampleTopology1();
+        topology.createSampleTopology2();
         modContext = new FloodlightModuleContext();
 
         floodLightProvider = createMock(IFloodlightProviderService.class);
@@ -104,6 +104,7 @@
         replay(sw1);
 
         sw1DevPort = 100;
+        sw1DevPort2 = 12L;
 
         odm = new OnosDeviceManager();
         /*
@@ -201,13 +202,11 @@
                 .setTargetProtocolAddress(IPv4.toIPv4AddressBytes("192.168.1.2")));
 
 
-        this.pktIn = new OFPacketIn()
-        .setInPort(sw1DevPort);
+        this.pktIn = new OFPacketIn().setInPort((short) sw1DevPort);
+
+        this.pktIn2 = new OFPacketIn().setInPort((short) sw1DevPort2);
 
         lastSeenTimestamp = new Date(1);
-
-        odm.init(modContext);
-        odm.startUp(modContext);
     }
 
     @Override
@@ -264,30 +263,46 @@
 
     /**
      * This test will invoke addOnosDevice to add a new device through Packet pkt1.
+     * @throws FloodlightModuleException
      */
     @Test
-    public void testProcessPacketInAddNewDevice() {
-        Ethernet eth = (Ethernet) pkt1;
-        Long longmac = eth.getSourceMAC().toLong();
-        OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
-
-        floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN), EasyMock.isA(OnosDeviceManager.class));
-        EasyMock.expectLastCall();
-        eventChannel.addEntry(longmac, srcDevice);
+    public void testProcessPacketInAddNewDevice() throws FloodlightModuleException {
+        floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN),
+                EasyMock.isA(OnosDeviceManager.class));
         EasyMock.expectLastCall();
         floodLightProvider.publishUpdate(EasyMock.isA(IUpdate.class));
         EasyMock.expectLastCall();
-        replay(floodLightProvider, eventChannel);
+        replay(floodLightProvider);
 
+        odm.init(modContext);
+        odm.startUp(modContext);
         Command cmd = odm.processPacketIn(sw1, pktIn, (Ethernet) pkt1);
         assertEquals(Command.CONTINUE, cmd);
 
-        verify(eventChannel);
+        EasyMock.verify(floodLightProvider);
     }
 
     /**
-     * This test will test return Command.STOP path in processPacketIn method
-     * by injecting a broadcast packet.
+     * Test ProcessPacket function.
+     * @throws FloodlightModuleException
+     */
+    @Test
+    public void testProcessPacketInHasLink() throws FloodlightModuleException {
+        floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN),
+                EasyMock.isA(OnosDeviceManager.class));
+        EasyMock.expectLastCall();
+        replay(floodLightProvider);
+
+        odm.init(modContext);
+        odm.startUp(modContext);
+        Command cmd = odm.processPacketIn(sw1, pktIn2, (Ethernet) pkt1);
+        assertEquals(Command.CONTINUE, cmd);
+
+        EasyMock.verify(floodLightProvider);
+    }
+
+    /**
+     * Test return Command.STOP path in processPacketIn method by injecting a broadcast packet.
      */
     @Test
     public void testProcessPacketInStop() {
@@ -296,99 +311,69 @@
     }
 
     /**
-     * This tests same packet received case.
-     */
-    @Test
-    public void testProcessPacketInSamePacket() {
-        Ethernet eth = (Ethernet) pkt2;
-        OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
-        odm.entryAdded(srcDevice);
-        srcDevice.setLastSeenTimestamp(lastSeenTimestamp);
-
-        Command cmd = odm.processPacketIn(sw1, pktIn, (Ethernet) pkt2);
-        assertEquals(Command.CONTINUE, cmd);
-        assertTrue(lastSeenTimestamp.before(srcDevice.getLastSeenTimestamp()));
-    }
-
-    /**
-     * This tests the packet with the same MAC but the second one without IP address.
-     */
-    @Test
-    public void testProcessPacketInNoIpAddress() {
-        Ethernet eth = (Ethernet) pkt3;
-        OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
-        odm.entryAdded(srcDevice);
-        srcDevice.setLastSeenTimestamp(lastSeenTimestamp);
-
-        Command cmd = odm.processPacketIn(sw1, pktIn, (Ethernet) pkt2);
-        assertEquals(Command.CONTINUE, cmd);
-        assertTrue(lastSeenTimestamp.before(srcDevice.getLastSeenTimestamp()));
-    }
-
-    /**
      * Test add a device from the information from packet.
+     * @throws FloodlightModuleException
      */
     @Test
-    public void testAddOnosDevice() {
+    public void testAddOnosDevice() throws FloodlightModuleException {
         Ethernet eth = (Ethernet) pkt1;
         Long longmac = eth.getSourceMAC().toLong();
         OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
 
         floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN), EasyMock.isA(OnosDeviceManager.class));
         EasyMock.expectLastCall();
-        eventChannel.addEntry(longmac, srcDevice);
-        EasyMock.expectLastCall();
         floodLightProvider.publishUpdate(EasyMock.isA(IUpdate.class));
         EasyMock.expectLastCall();
-        replay(floodLightProvider, eventChannel);
+        replay(floodLightProvider);
 
+        odm.init(modContext);
+        odm.startUp(modContext);
         odm.addOnosDevice(longmac, srcDevice);
 
-        verify(eventChannel);
+        EasyMock.verify(floodLightProvider);
     }
 
     /**
      * Test delete a device.
+     * @throws FloodlightModuleException
      */
     @Test
-    public void testDeleteOnosDevice() {
+    public void testDeleteOnosDevice() throws FloodlightModuleException {
         Ethernet eth = (Ethernet) pkt1;
-        Long longmac = eth.getSourceMAC().toLong();
         OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
 
         floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN), EasyMock.isA(OnosDeviceManager.class));
         EasyMock.expectLastCall();
-        eventChannel.removeEntry(longmac);
-        EasyMock.expectLastCall();
         floodLightProvider.publishUpdate(EasyMock.isA(IUpdate.class));
         EasyMock.expectLastCall();
-        replay(floodLightProvider, eventChannel);
+        replay(floodLightProvider);
 
+        odm.init(modContext);
+        odm.startUp(modContext);
         odm.deleteOnosDevice(srcDevice);
 
-        verify(eventChannel);
+        EasyMock.verify(floodLightProvider);
     }
 
     /**
      * Test delete a device by using its source mac address.
+     * @throws FloodlightModuleException
      */
     @Test
-    public void testDeleteOnosDeviceByMac() {
+    public void testDeleteOnosDeviceByMac() throws FloodlightModuleException {
         Ethernet eth = (Ethernet) pkt1;
         MACAddress mac = eth.getSourceMAC();
-        Long longmac = mac.toLong();
-        OnosDevice srcDevice = odm.getSourceDeviceFromPacket(eth, sw1Dpid, sw1DevPort);
 
         floodLightProvider.addOFMessageListener(EasyMock.eq(OFType.PACKET_IN), EasyMock.isA(OnosDeviceManager.class));
         EasyMock.expectLastCall();
-        eventChannel.removeEntry(longmac);
-        EasyMock.expectLastCall();
         floodLightProvider.publishUpdate(EasyMock.isA(IUpdate.class));
         EasyMock.expectLastCall();
-        replay(floodLightProvider, eventChannel);
+        replay(floodLightProvider);
 
-        odm.entryAdded(srcDevice);
+        odm.init(modContext);
+        odm.startUp(modContext);
         odm.deleteOnosDeviceByMac(mac);
-        verify(eventChannel);
+
+        EasyMock.verify(floodLightProvider);
     }
 }
diff --git a/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceTest.java b/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceTest.java
new file mode 100644
index 0000000..6c79bf0
--- /dev/null
+++ b/src/test/java/net/onrc/onos/core/devicemanager/OnosDeviceTest.java
@@ -0,0 +1,65 @@
+package net.onrc.onos.core.devicemanager;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.Date;
+
+import net.floodlightcontroller.util.MACAddress;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+/*
+ * This is the test for OnosDevice.class.
+ */
+public class OnosDeviceTest {
+
+    MACAddress mac1;
+    MACAddress mac2;
+    Long dpid1;
+    Long dpid2;
+    Long portNum1;
+    Long portNum2;
+    Date date1;
+    Date date2;
+
+    @Before
+    public void setUp() throws Exception {
+        mac1 = MACAddress.valueOf("00:00:00:00:00:01");
+        mac2 = MACAddress.valueOf("00:00:00:00:00:01");
+        dpid1 = 1L;
+        dpid2 = 1L;
+        portNum1 = 1L;
+        portNum2 = 1L;
+        date1 = new Date(1L);
+        date2 = new Date(2L);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+    }
+
+    /*
+     * Test for making sure hashCode function works properly.
+     */
+    @Test
+    public void testHashCode() {
+        OnosDevice dev1 = new OnosDevice(mac1, null, dpid1, portNum1, date1);
+        OnosDevice dev2 = new OnosDevice(mac2, null, dpid2, portNum2, date2);
+
+        assertTrue(dev1.hashCode() == dev2.hashCode());
+    }
+
+    /*
+     * Test for making sure equals function works properly.
+     */
+    @Test
+    public void testEqualsObject() {
+        OnosDevice dev1 = new OnosDevice(mac1, null, dpid1, portNum1, date1);
+        OnosDevice dev2 = new OnosDevice(mac2, null, dpid2, portNum2, date2);
+
+        assertTrue(dev1.equals(dev2));
+    }
+
+}
diff --git a/src/test/java/net/onrc/onos/core/intent/ConstrainedBFSTreeTest.java b/src/test/java/net/onrc/onos/core/intent/ConstrainedBFSTreeTest.java
index 4a58b90..9a3aaa2 100644
--- a/src/test/java/net/onrc/onos/core/intent/ConstrainedBFSTreeTest.java
+++ b/src/test/java/net/onrc/onos/core/intent/ConstrainedBFSTreeTest.java
@@ -5,6 +5,7 @@
 import static org.junit.Assert.assertNull;
 import net.onrc.onos.core.intent.IntentOperation.Operator;
 import net.onrc.onos.core.topology.LinkEvent;
+import net.onrc.onos.core.topology.MockTopology;
 
 import org.junit.After;
 import org.junit.Before;
diff --git a/src/test/java/net/onrc/onos/core/intent/MockTopology.java b/src/test/java/net/onrc/onos/core/intent/MockTopology.java
deleted file mode 100644
index ddbdbe7..0000000
--- a/src/test/java/net/onrc/onos/core/intent/MockTopology.java
+++ /dev/null
@@ -1,86 +0,0 @@
-package net.onrc.onos.core.intent;
-
-import net.onrc.onos.core.topology.Link;
-import net.onrc.onos.core.topology.LinkImpl;
-import net.onrc.onos.core.topology.Switch;
-import net.onrc.onos.core.topology.SwitchImpl;
-import net.onrc.onos.core.topology.TopologyImpl;
-
-/**
- * A mock class of Topology.
- * This class should be used only by test codes.
- */
-public class MockTopology extends TopologyImpl {
-    // TODO this class doesn't seem like it should extend TopologyImpl. It
-    // isn't a Topology, it's more of a TopologyBuilder - methods to
-    // create an populate a fake topology that's not based on discovery
-    // data from the driver modules.
-    // We may well need a MockTopology, but that's not what this class is
-    // doing.
-
-    public static final Long LOCAL_PORT = 0xFFFEL;
-    public SwitchImpl sw1, sw2, sw3, sw4;
-
-    public Switch addSwitch(Long switchId) {
-        SwitchImpl sw = new SwitchImpl(this, switchId);
-        this.putSwitch(sw);
-        return sw;
-    }
-
-    public Link[] addBidirectionalLinks(Long srcDpid, Long srcPortNo, Long dstDpid, Long dstPortNo) {
-        Link[] links = new Link[2];
-        links[0] = new LinkImpl(this, getPort(srcDpid, srcPortNo), getPort(dstDpid, dstPortNo));
-        links[1] = new LinkImpl(this, getPort(dstDpid, dstPortNo), getPort(srcDpid, srcPortNo));
-
-        putLink(links[0]);
-        putLink(links[1]);
-
-        return links;
-    }
-
-    /**
-     * create sample topology of 4 switches and 5 bidirectional links.
-     * <pre>
-     * [1] --- [2]
-     *  |    /  |
-     *  |  /    |
-     * [4] --- [3]
-     * </pre>
-     */
-    public void createSampleTopology1() {
-        sw1 = (SwitchImpl) addSwitch(1L);
-        sw1.addPort(LOCAL_PORT);
-        sw2 = (SwitchImpl) addSwitch(2L);
-        sw2.addPort(LOCAL_PORT);
-        sw3 = (SwitchImpl) addSwitch(3L);
-        sw3.addPort(LOCAL_PORT);
-        sw4 = (SwitchImpl) addSwitch(4L);
-        sw4.addPort(LOCAL_PORT);
-
-        sw1.addPort(12L); // sw1 -> sw2
-        sw1.addPort(14L); // sw1 -> sw4
-        sw2.addPort(21L); // sw2 -> sw1
-        sw2.addPort(23L); // sw2 -> sw3
-        sw2.addPort(24L); // sw2 -> sw4
-        sw3.addPort(32L); // sw3 -> sw2
-        sw3.addPort(34L); // sw3 -> sw4
-        sw4.addPort(41L); // sw4 -> sw1
-        sw4.addPort(42L); // sw4 -> sw2
-        sw4.addPort(43L); // sw4 -> sw3
-
-        addBidirectionalLinks(1L, 12L, 2L, 21L);
-        addBidirectionalLinks(2L, 23L, 3L, 32L);
-        addBidirectionalLinks(3L, 34L, 4L, 43L);
-        addBidirectionalLinks(4L, 41L, 1L, 14L);
-        addBidirectionalLinks(2L, 24L, 4L, 42L);
-
-        // set capacity of all links to 1000Mbps
-        for (Link link : getLinks()) {
-            ((LinkImpl) link).setCapacity(1000.0);
-        }
-    }
-
-    public void removeLink(Long srcDpid, Long srcPortNo, Long dstDpid, Long dstPortNo) {
-        removeLink(getLink(srcDpid, srcPortNo, dstDpid, dstPortNo));
-    }
-}
diff --git a/src/test/java/net/onrc/onos/core/intent/runtime/IntentTestMocks.java b/src/test/java/net/onrc/onos/core/intent/runtime/IntentTestMocks.java
index 1a2e1c5..a6dde8b 100644
--- a/src/test/java/net/onrc/onos/core/intent/runtime/IntentTestMocks.java
+++ b/src/test/java/net/onrc/onos/core/intent/runtime/IntentTestMocks.java
@@ -1,19 +1,5 @@
 package net.onrc.onos.core.intent.runtime;
 
-
-import net.floodlightcontroller.core.module.FloodlightModuleContext;
-import net.floodlightcontroller.restserver.IRestApiService;
-import net.onrc.onos.core.datagrid.IDatagridService;
-import net.onrc.onos.core.datagrid.IEventChannel;
-import net.onrc.onos.core.datagrid.IEventChannelListener;
-import net.onrc.onos.core.intent.IntentOperationList;
-import net.onrc.onos.core.intent.MockTopology;
-import net.onrc.onos.core.intent.runtime.web.IntentWebRoutable;
-import net.onrc.onos.core.registry.IControllerRegistryService;
-import net.onrc.onos.core.topology.ITopologyListener;
-import net.onrc.onos.core.topology.ITopologyService;
-import org.powermock.api.easymock.PowerMock;
-
 import static org.easymock.EasyMock.anyObject;
 import static org.easymock.EasyMock.createMock;
 import static org.easymock.EasyMock.eq;
@@ -21,6 +7,19 @@
 import static org.easymock.EasyMock.expectLastCall;
 import static org.easymock.EasyMock.replay;
 import static org.easymock.EasyMock.verify;
+import net.floodlightcontroller.core.module.FloodlightModuleContext;
+import net.floodlightcontroller.restserver.IRestApiService;
+import net.onrc.onos.core.datagrid.IDatagridService;
+import net.onrc.onos.core.datagrid.IEventChannel;
+import net.onrc.onos.core.datagrid.IEventChannelListener;
+import net.onrc.onos.core.intent.IntentOperationList;
+import net.onrc.onos.core.intent.runtime.web.IntentWebRoutable;
+import net.onrc.onos.core.registry.IControllerRegistryService;
+import net.onrc.onos.core.topology.ITopologyListener;
+import net.onrc.onos.core.topology.ITopologyService;
+import net.onrc.onos.core.topology.MockTopology;
+
+import org.powermock.api.easymock.PowerMock;
 
 /**
  * This class contains all of the mocked code required to run a test that uses
diff --git a/src/test/java/net/onrc/onos/core/intent/runtime/PathCalcRuntimeModuleTest.java b/src/test/java/net/onrc/onos/core/intent/runtime/PathCalcRuntimeModuleTest.java
index 9623436..5d4adb8 100644
--- a/src/test/java/net/onrc/onos/core/intent/runtime/PathCalcRuntimeModuleTest.java
+++ b/src/test/java/net/onrc/onos/core/intent/runtime/PathCalcRuntimeModuleTest.java
@@ -17,10 +17,10 @@
 import net.onrc.onos.core.intent.IntentMap;
 import net.onrc.onos.core.intent.IntentOperation.Operator;
 import net.onrc.onos.core.intent.IntentOperationList;
-import net.onrc.onos.core.intent.MockTopology;
 import net.onrc.onos.core.intent.ShortestPathIntent;
 import net.onrc.onos.core.topology.DeviceEvent;
 import net.onrc.onos.core.topology.LinkEvent;
+import net.onrc.onos.core.topology.MockTopology;
 import net.onrc.onos.core.topology.PortEvent;
 import net.onrc.onos.core.topology.SwitchEvent;
 
diff --git a/src/test/java/net/onrc/onos/core/intent/runtime/UseCaseTest.java b/src/test/java/net/onrc/onos/core/intent/runtime/UseCaseTest.java
index d911d2f..76af2ec 100644
--- a/src/test/java/net/onrc/onos/core/intent/runtime/UseCaseTest.java
+++ b/src/test/java/net/onrc/onos/core/intent/runtime/UseCaseTest.java
@@ -24,7 +24,6 @@
 import net.onrc.onos.core.intent.Intent.IntentState;
 import net.onrc.onos.core.intent.IntentOperation.Operator;
 import net.onrc.onos.core.intent.IntentOperationList;
-import net.onrc.onos.core.intent.MockTopology;
 import net.onrc.onos.core.intent.PathIntent;
 import net.onrc.onos.core.intent.PathIntentMap;
 import net.onrc.onos.core.intent.ShortestPathIntent;
@@ -34,6 +33,7 @@
 import net.onrc.onos.core.topology.ITopologyListener;
 import net.onrc.onos.core.topology.ITopologyService;
 import net.onrc.onos.core.topology.LinkEvent;
+import net.onrc.onos.core.topology.MockTopology;
 import net.onrc.onos.core.topology.PortEvent;
 import net.onrc.onos.core.topology.SwitchEvent;
 import net.onrc.onos.core.topology.Topology;
diff --git a/src/test/java/net/onrc/onos/core/topology/MockTopology.java b/src/test/java/net/onrc/onos/core/topology/MockTopology.java
new file mode 100644
index 0000000..888779a
--- /dev/null
+++ b/src/test/java/net/onrc/onos/core/topology/MockTopology.java
@@ -0,0 +1,140 @@
+package net.onrc.onos.core.topology;
+
+import net.floodlightcontroller.util.MACAddress;
+
+/**
+ * A mock class of Topology.
+ * This class should be used only by test codes.
+ */
+public class MockTopology extends TopologyImpl {
+    // TODO this class doesn't seem like it should extend TopologyImpl. It
+    // isn't a Topology, it's more of a TopologyBuilder - methods to
+    // create an populate a fake topology that's not based on discovery
+    // data from the driver modules.
+    // We may well need a MockTopology, but that's not what this class is
+    // doing.
+
+    public static final Long LOCAL_PORT = 0xFFFEL;
+    public SwitchImpl sw1, sw2, sw3, sw4;
+
+    public Switch addSwitch(Long switchId) {
+        SwitchImpl sw = new SwitchImpl(this, switchId);
+        this.putSwitch(sw);
+        return sw;
+    }
+
+    public Link[] addBidirectionalLinks(Long srcDpid, Long srcPortNo, Long dstDpid, Long dstPortNo) {
+        Link[] links = new Link[2];
+        links[0] = new LinkImpl(this, getPort(srcDpid, srcPortNo), getPort(dstDpid, dstPortNo));
+        links[1] = new LinkImpl(this, getPort(dstDpid, dstPortNo), getPort(srcDpid, srcPortNo));
+
+        putLink(links[0]);
+        putLink(links[1]);
+
+        return links;
+    }
+
+    /**
+     * create sample topology of 4 switches and 5 bidirectional links.
+     * <pre>
+     * [1] --- [2]
+     *  |    /  |
+     *  |  /    |
+     * [4] --- [3]
+     * </pre>
+     */
+    public void createSampleTopology1() {
+        sw1 = (SwitchImpl) addSwitch(1L);
+        sw1.addPort(LOCAL_PORT);
+        sw2 = (SwitchImpl) addSwitch(2L);
+        sw2.addPort(LOCAL_PORT);
+        sw3 = (SwitchImpl) addSwitch(3L);
+        sw3.addPort(LOCAL_PORT);
+        sw4 = (SwitchImpl) addSwitch(4L);
+        sw4.addPort(LOCAL_PORT);
+
+        sw1.addPort(12L); // sw1 -> sw2
+        sw1.addPort(14L); // sw1 -> sw4
+        sw2.addPort(21L); // sw2 -> sw1
+        sw2.addPort(23L); // sw2 -> sw3
+        sw2.addPort(24L); // sw2 -> sw4
+        sw3.addPort(32L); // sw3 -> sw2
+        sw3.addPort(34L); // sw3 -> sw4
+        sw4.addPort(41L); // sw4 -> sw1
+        sw4.addPort(42L); // sw4 -> sw2
+        sw4.addPort(43L); // sw4 -> sw3
+
+        addBidirectionalLinks(1L, 12L, 2L, 21L);
+        addBidirectionalLinks(2L, 23L, 3L, 32L);
+        addBidirectionalLinks(3L, 34L, 4L, 43L);
+        addBidirectionalLinks(4L, 41L, 1L, 14L);
+        addBidirectionalLinks(2L, 24L, 4L, 42L);
+
+        // set capacity of all links to 1000Mbps
+        for (Link link : getLinks()) {
+            ((LinkImpl) link).setCapacity(1000.0);
+        }
+    }
+
+    /**
+     * create sample topology of 4 switches and 5 bidirectional links.
+     * <pre>
+     *
+     *
+     * [H1]-[1] --- [2]
+     *       |    /  |
+     *       |  /    |
+     *      [4] --- [3]-[H3]
+     * </pre>
+     */
+    public void createSampleTopology2() {
+        sw1 = (SwitchImpl) addSwitch(1L);
+        sw1.addPort(LOCAL_PORT);
+        sw2 = (SwitchImpl) addSwitch(2L);
+        sw2.addPort(LOCAL_PORT);
+        sw3 = (SwitchImpl) addSwitch(3L);
+        sw3.addPort(LOCAL_PORT);
+        sw4 = (SwitchImpl) addSwitch(4L);
+        sw4.addPort(LOCAL_PORT);
+
+        Port port12 = sw1.addPort(12L); // sw1 -> sw2
+        Port port14 = sw1.addPort(14L); // sw1 -> sw4
+        Port port15 = sw1.addPort(15L); // sw1 -> h1
+        Port port21 = sw2.addPort(21L); // sw2 -> sw1
+        Port port23 = sw2.addPort(23L); // sw2 -> sw3
+        Port port24 = sw2.addPort(24L); // sw2 -> sw4
+        Port port32 = sw3.addPort(32L); // sw3 -> sw2
+        Port port34 = sw3.addPort(34L); // sw3 -> sw4
+        Port port35 = sw3.addPort(35L); // sw3 -> h3
+        Port port41 = sw4.addPort(41L); // sw4 -> sw1
+        Port port42 = sw4.addPort(42L); // sw4 -> sw2
+        Port port43 = sw4.addPort(43L); // sw4 -> sw3
+
+        MACAddress mac1 = MACAddress.valueOf("00:44:33:22:11:00");
+        DeviceImpl dev1 = new DeviceImpl(this, mac1);
+        dev1.addAttachmentPoint(port15);
+        dev1.setLastSeenTime(1L);
+        this.putDevice(dev1);
+
+        MACAddress mac3 = MACAddress.valueOf("00:11:22:33:44:55");
+        DeviceImpl dev3 = new DeviceImpl(this, mac3);
+        dev3.addAttachmentPoint(port35);
+        dev3.setLastSeenTime(1L);
+        this.putDevice(dev3);
+
+        addBidirectionalLinks(1L, 12L, 2L, 21L);
+        addBidirectionalLinks(2L, 23L, 3L, 32L);
+        addBidirectionalLinks(3L, 34L, 4L, 43L);
+        addBidirectionalLinks(4L, 41L, 1L, 14L);
+        addBidirectionalLinks(2L, 24L, 4L, 42L);
+
+        // set capacity of all links to 1000Mbps
+        for (Link link : getLinks()) {
+            ((LinkImpl) link).setCapacity(1000.0);
+        }
+    }
+
+    public void removeLink(Long srcDpid, Long srcPortNo, Long dstDpid, Long dstPortNo) {
+        removeLink(getLink(srcDpid, srcPortNo, dstDpid, dstPortNo));
+    }
+}